Baseball glossary
Baseball terms, explained in plain English
Every word you are likely to hear at the ballpark, on a broadcast, or from a coach, in 145 short definitions you can read in a few seconds each.
This glossary is for anyone who is new to the game or wants to keep up: first-time players, parents in the stands, adults joining a rec league, and volunteer coaches explaining the rules to a young team. Terms are listed from A to Z, and related terms are linked so you can follow a topic from one entry to the next.
Almost every term here also applies to softball. A handful of softball-only terms, like the DP/flex, slap hitter, windmill, slowpitch arc, and extra player (EP), are included too and marked as softball terms. Where pro rules differ from youth and rec play, the definition says so.
145 terms, A to Z.
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A
- At-bat
- A batter's turn at the plate that counts toward batting average. Walks, hit-by-pitches, sacrifices, and catcher's interference are plate appearances but not at-bats. See also: Plate appearance, Batting average
B
- Backstop
- The fence or screen behind home plate that stops wild pitches and foul balls from leaving the field and protects spectators.
- Backwards K
- The scorekeeping mark for a strikeout where the batter took strike three without swinging, known as a called strikeout or striking out looking. See also: K, Strikeout
- Balk
- An illegal motion by the pitcher with runners on base, such as starting the delivery and stopping, or faking a throw to first base. Every runner moves up one base. Softball has no balk; a similar mistake is called an illegal pitch. See also: Pickoff, Rubber
- Ball
- A pitch outside the strike zone that the batter does not swing at. Four balls in one plate appearance give the batter a walk.
- Baltimore chop
- A batted ball hit hard into the ground in front of the plate that bounces so high the batter often reaches first before anyone can make a play.
- Bases
- The four stations a runner must touch in order to score: first, second, third, and home. In baseball they are 90 feet apart at the high school level and up, and closer together in youth leagues.
- Bases loaded
- Runners on first, second, and third base at the same time. A walk or hit by pitch then forces in a run. See also: Ducks on the pond, Grand slam
- Batter's box
- The chalk rectangles on either side of home plate where the batter must stand to hit. There is one for right-handed and one for left-handed hitters.
- Battery
- The pitcher and catcher together. They work as a pair to decide which pitches to throw. See also: Pitcher, Catcher
- Batting average
- Hits divided by at-bats, written as a three-digit decimal. A .300 hitter gets a hit in about three of every ten at-bats.
- Batting order
- The fixed sequence in which a team's players take turns at bat. It stays the same all game, and substitutes take the spot of the player they replace. See also: Lineup card, Leadoff hitter, Cleanup hitter
- Bottom of the inning
- The second half of an inning, when the home team bats.
- Bullpen
- The area where relief pitchers warm up during a game. The word also refers to a team's group of relievers as a whole. See also: Relief pitcher, Closer
- Bunt
- Holding the bat out and tapping the pitch softly into the infield instead of swinging. It is used to move runners up or to surprise the defense for a hit. See also: Sacrifice bunt, Squeeze play
C
- Can of corn
- Slang for an easy, high fly ball that an outfielder catches without having to move much.
- Catcher
- The player who crouches behind home plate, receives pitches, and calls signals for the pitcher. Position number 2.
- Center field
- The middle of the three outfield positions, usually covering the most ground. Position number 8.
- Changeup
- A pitch thrown with the same arm motion as a fastball but noticeably slower, meant to throw off the batter's timing.
- Check swing
- A swing the batter starts but stops partway. If the umpire rules the batter went too far, it counts as a strike.
- Chin music
- Slang for a pitch thrown high and inside, close to the batter's head or upper body. Throwing at a batter on purpose can get a pitcher ejected.
- Cleanup hitter
- The batter in the fourth spot in the order, traditionally a power hitter expected to drive in runners who reached base ahead of them.
- Closer
- The relief pitcher a team trusts to get the final outs of a close game it is leading. See also: Save, Relief pitcher
- Corner infielders
- The first baseman and third baseman, who play near the foul lines at the corners of the infield.
- Count
- The number of balls and strikes on the batter, always said balls first. A 3-2 count, three balls and two strikes, is called a full count. See also: Ball, Strike
- Curveball
- A breaking pitch thrown with topspin so it dives downward, and often sideways, as it reaches the plate. See also: Uncle Charlie, Slider
- Cutter
- A cut fastball. It is thrown almost as hard as a fastball but breaks a few inches toward the pitcher's glove side late in its flight.
- Cycle
- When one batter gets a single, double, triple, and home run in the same game. It is one of the rarer feats in the sport.
D
- Delayed steal
- A steal where the runner waits until the defense relaxes, often as the catcher throws the ball back, before breaking for the next base. See also: Steal
- Designated hitter
- A player who bats in place of the pitcher and does not play in the field. MLB has used the DH in both leagues since 2022; youth and rec leagues set their own rules. See also: Pinch hitter, Extra player (EP)
- Diamond
- The infield, named for the diamond shape formed by the four bases. People also use it to mean the whole field.
- Dinger
- Slang for a home run. See also: Home run
- Double
- A hit on which the batter safely reaches second base.
- Double play
- A single play that gets two outs, such as a ground ball thrown to second and then on to first. A 6-4-3 double play goes shortstop to second baseman to first baseman. See also: Triple play, Position numbers
- DP/Flex
- Softball term. In fastpitch, the designated player (DP) bats for the flex player, who plays defense only. Depending on the rules in use, the two can swap roles during the game without using up a substitution. See also: Designated hitter
- Dropped third strike
- If the catcher does not cleanly catch strike three, the batter can try to run to first. This is allowed only when first base is empty or there are two outs, and many young-player leagues turn the rule off. See also: Strikeout
- Ducks on the pond
- Slang for runners on base, especially with the bases loaded, waiting to be driven in.
- Dugout
- The bench area for each team, usually sunk partly below field level, along the first- or third-base line.
E
- Earned run
- A run that scores without the help of an error or passed ball. Only earned runs count against a pitcher's ERA. See also: ERA, Error
- ERA
- Earned run average: the number of earned runs a pitcher allows per nine innings. Leagues with shorter games, like seven innings, sometimes calculate it per seven. See also: Earned run, WHIP
- Error
- A misplay by a fielder, such as a dropped catch or bad throw, that lets a batter or runner reach base or advance when an ordinary play would have stopped them.
- Extra innings
- Additional innings played when the score is tied after the regulation number. In the MLB regular season, each extra half-inning starts with a runner on second base; many youth and rec leagues use time limits or allow ties instead.
- Extra player (EP)
- Softball term. An extra batter in the lineup who does not have to play in the field, common in rec and slowpitch leagues. Some leagues allow more than one EP. See also: DP/Flex, Designated hitter
F
- Fair ball
- A batted ball that lands, or is touched, in fair territory, between and including the foul lines. Fair balls are in play.
- Fastball
- The most common pitch: thrown as hard as possible with little break. Most pitchers throw several versions. See also: Four-seam fastball, Two-seam fastball, Cheese
- Fielder's choice
- When the defense chooses to put out a different runner instead of the batter, who reaches base. The batter is charged with an at-bat but not credited with a hit.
- First base
- The first bag a batter runs to, and the player who covers it. The first baseman is position number 3.
- Fly ball
- A batted ball hit high into the air. If a fielder catches it before it lands, the batter is out.
- Force out
- An out made by touching a base before the runner gets there when that runner had to advance because the batter became a runner. No tag is needed. See also: Tag out
- Foul ball
- A batted ball that ends up in foul territory. It counts as a strike unless the batter already has two strikes, in which case the count stays the same, except on a bunt. See also: Foul lines, Foul tip
- Foul lines
- The two white lines running from home plate past first and third base to the outfield wall. The lines themselves are fair territory.
- Foul pole
- The tall pole at the end of each foul line on the outfield wall. A fly ball that hits it is a fair ball and usually a home run.
- Foul tip
- A pitch the batter barely nicks that goes sharply and directly into the catcher's glove and is caught. It is treated like a swinging strike, so it can be strike three. See also: Foul ball
- Four-seam fastball
- A fastball gripped across the seams so all four seams spin through the air. It is usually a pitcher's fastest and straightest pitch.
- Frozen rope
- Slang for a line drive hit so hard and flat it looks like a rope stretched tight.
G
- Golden sombrero
- Slang for striking out four times in one game.
- Grand slam
- A home run hit with the bases loaded, scoring four runs. See also: Bases loaded, Home run
- Ground ball
- A batted ball that bounces or rolls along the ground. Also called a grounder.
H
- Heat
- Slang for a very fast fastball, as in a pitcher who "brings the heat."
- Hit
- Reaching base safely on a batted ball without the help of an error or fielder's choice. Singles, doubles, triples, and home runs are all hits.
- Hit and run
- A play where the runner starts for the next base as the pitch is thrown and the batter tries to put the ball in play, ideally through a gap left by a fielder covering the base.
- Hit by pitch
- When a pitch hits the batter, who is awarded first base. It is scored as HBP and counts as a plate appearance but not an at-bat.
- Hold
- A stat for a relief pitcher who enters in a save situation, keeps the lead, and leaves the game without finishing it. See also: Save
- Home plate
- The five-sided rubber slab where the batter stands and where runners finish to score a run.
- Home run
- A hit that lets the batter circle all the bases and score, usually by hitting the ball over the outfield fence in fair territory. See also: Grand slam, Inside-the-park home run, Dinger
I
- Infield
- The dirt and grass area inside and around the four bases, and the four fielders who play there: first base, second base, shortstop, and third base.
- Infield dirt
- The skinned area of the infield where the fielders and runners play, as opposed to the grass. Some fields, especially in softball, are all dirt.
- Infield fly rule
- With fewer than two outs and runners on first and second, or the bases loaded, a fair pop-up an infielder can catch with ordinary effort is ruled an automatic out. It stops fielders from dropping the ball on purpose to start a double play. See also: Pop-up, Double play
- Inning
- A unit of the game in which each team bats until it makes three outs. Pro and college baseball play nine innings; youth and softball games are often six or seven. See also: Top of the inning, Bottom of the inning
- Inside-the-park home run
- A home run on a ball that stays in the field of play, where the batter runs all the way around before the defense can make a play.
- Intentional walk
- Walking a batter on purpose to avoid a dangerous hitter or set up a force out. In MLB and many other levels, the manager can simply signal for it without any pitches being thrown. See also: Walk
K
- K
- The scorekeeping symbol for a strikeout. A forward K means the batter struck out swinging. See also: Backwards K, Strikeout
- Knuckleball
- A slow pitch thrown with almost no spin, so it flutters and moves unpredictably on the way to the plate. It is hard for batters and catchers alike.
L
- Lead
- The few steps a runner takes off a base before the pitch to get closer to the next one.
- Leadoff hitter
- The first batter in the lineup, or the first batter of any inning. Teams usually want someone who gets on base often in the top spot.
- Left field
- The outfield position on the third-base side. Position number 7.
- Line drive
- A hard-hit ball that travels on a low, fairly straight path rather than arcing high or bouncing.
- Lineup card
- The written list of a team's batting order and fielding positions, handed to the umpire and opposing team before the game.
M
- Meatball
- Slang for an easy pitch right over the middle of the plate that is easy to hit hard.
- Mercy rule
- A rule that ends a game early when one team is ahead by a large margin after a set number of innings. Also called the run-ahead rule; it is common in youth, high school, and rec play, and the margins vary by league.
- Middle infield
- The second baseman and shortstop, who play up the middle on either side of second base and handle most double plays. See also: Shortstop, Second base
- Mound
- The raised dirt hill in the middle of the infield where the pitcher stands. In pro baseball it is 10 inches high and the rubber is 60 feet, 6 inches from home plate; youth fields are smaller. See also: Rubber, Pitching circle
N
- No-hitter
- A complete game in which one team gets no hits. Batters can still reach base on walks or errors. See also: Perfect game
O
- On-base percentage
- How often a batter reaches base, counting hits, walks, and hit-by-pitches, divided by plate appearances (with sacrifice bunts left out). Shortened to OBP.
- On-deck circle
- The marked circle near the dugout where the next batter waits and takes practice swings.
- OPS
- On-base plus slugging: a player's on-base percentage and slugging percentage added together. It is a quick way to sum up a hitter's overall production. See also: On-base percentage, Slugging percentage
- Out
- When a batter or runner is retired and must leave the bases. Three outs end a team's half of the inning.
- Outfield
- The grass area beyond the infield, and the three players who cover it: left field, center field, and right field.
P
- Painting the corners
- Pitching to the very edges of the strike zone, where strikes are hardest to hit well.
- Passed ball
- A catchable pitch the catcher fails to hold, letting a runner move up. It is charged to the catcher.
- Perfect game
- A complete game in which no batter on one team reaches base at all: no hits, walks, hit batters, or errors that put anyone on. See also: No-hitter
- Pickoff
- A throw from the pitcher or catcher to a base to tag out a runner who has taken too big a lead. See also: Lead, Balk
- Pinch hitter
- A substitute who bats in place of a player in the lineup. The replaced player usually cannot return, though many rec leagues allow free substitution.
- Pinch runner
- A substitute who takes over for a player who is already on base, often to add speed.
- Pitch clock
- A timer that limits how long a pitcher can take between pitches. In MLB it is 15 seconds with the bases empty and 18 seconds with runners on; a violation adds a ball, and a batter who is not ready is charged a strike.
- Pitch count
- The number of pitches a pitcher has thrown in a game. Many youth leagues set daily limits and required rest days based on it to protect young arms.
- Pitcher
- The player who throws each pitch to the batter from the mound. Position number 1.
- Pitching circle
- Softball term. The flat circle around the pitcher's plate in softball, 8 feet in radius in fastpitch. Softball has no raised mound.
- Plate appearance
- Any completed turn at bat, whatever the result. Unlike an at-bat, it includes walks, hit-by-pitches, and sacrifices. See also: At-bat
- Pop-up
- A batted ball hit very high but not very far, usually caught by an infielder or catcher.
- Position numbers
- Scorekeepers number the fielding positions: pitcher 1, catcher 2, first base 3, second base 4, third base 5, shortstop 6, left field 7, center field 8, and right field 9. Slowpitch softball often adds a tenth fielder. See also: Double play
Q
- Quality start
- A starting pitcher's outing of at least six innings while allowing three or fewer earned runs.
R
- Rally
- A run of hits and baserunners that leads to several runs in an inning, often to catch up or take the lead.
- RBI
- Run batted in: credit to a batter for each run that scores as a result of their plate appearance, such as on a hit, a sacrifice fly, or a bases-loaded walk. No RBI is given on a run that scores on an error or a double play ground ball.
- Relief pitcher
- A pitcher who comes into the game after the starter has left. Also called a reliever. See also: Bullpen, Closer, Starting pitcher
- Right field
- The outfield position on the first-base side. Position number 9.
- Rubber
- The rectangular white slab on top of the mound that the pitcher must keep a foot on when starting a pitch. Also called the pitching rubber or pitcher's plate.
- Run
- The point scored when a runner touches all four bases and crosses home plate safely.
S
- Sacrifice bunt
- A bunt that moves a runner up a base while the batter is thrown out. The batter is not charged with an at-bat.
- Sacrifice fly
- A fly ball caught for an out that lets a runner tag up and score. The batter gets an RBI and is not charged with an at-bat. See also: Tag up, RBI
- Safe
- The umpire's call when a runner reaches a base before being tagged or forced out.
- Save
- Credit to a relief pitcher who finishes a win while protecting a close lead, generally three runs or fewer, or with the potential tying run on base, at bat, or on deck. See also: Closer, Hold
- Second base
- The base across the diamond from home plate, and the infielder who plays to the right of it. The second baseman is position number 4.
- Shift
- Moving fielders out of their usual spots to where a batter tends to hit. MLB limited shifts in 2023 by requiring two infielders on each side of second base, all on the dirt.
- Shortstop
- The infielder who plays between second and third base, usually the busiest and most athletic fielder. Position number 6.
- Single
- A hit on which the batter safely reaches first base.
- Sinker
- A fastball that drops and tails toward the pitcher's arm side, designed to get batters to hit ground balls.
- Slap hitter
- Softball term. A fastpitch hitter, usually left-handed, who starts moving toward first base during the swing and slaps or bunts the ball on the ground to use their speed.
- Slider
- A breaking pitch thrown harder than a curveball that breaks sharply sideways and slightly down late in its path.
- Slowpitch arc
- Softball term. In slowpitch, each pitch must travel in a high arc, with a minimum and maximum height set by the league, often in the range of 6 to 12 feet off the ground.
- Slugging percentage
- Total bases divided by at-bats. A single counts 1, a double 2, a triple 3, and a home run 4, so it measures a hitter's power. See also: OPS
- Splitter
- A split-finger fastball, gripped with the fingers spread wide, that looks like a fastball and then drops sharply near the plate.
- Squeeze play
- A bunt with a runner on third, who breaks for home to score as the batter lays the ball down. See also: Sacrifice bunt, Bunt
- Starting pitcher
- The pitcher who begins the game for a team. Starters usually pitch several innings before handing off to relievers.
- Steal
- When a runner advances to the next base on a pitch without the ball being hit. A successful one is a stolen base. Youth and softball leagues often restrict when runners can leave the base. See also: Delayed steal, Lead
- Strike
- A pitch in the strike zone that the batter takes, any pitch the batter swings at and misses, or a foul ball with fewer than two strikes. Three strikes is a strikeout.
- Strike zone
- The area over home plate, roughly from the midpoint of the batter's torso down to the hollow beneath the kneecaps, where a pitch is called a strike. Exact definitions vary a little between baseball and softball levels.
- Strikeout
- An out made when a batter gets three strikes. It is scored as a K. See also: K, Backwards K, Dropped third strike
T
- Tag out
- Putting out a runner by touching them with the ball, or a glove holding the ball, while they are off a base.
- Tag up
- When a fly ball is caught, a runner must touch their original base after the catch before advancing. Leaving early can lead to an out on an appeal. See also: Sacrifice fly
- Texas leaguer
- Slang for a weak fly ball that drops in for a hit between the infielders and outfielders. Also called a bloop.
- Third base
- The last base before home, and the infielder who covers it. The third baseman is position number 5.
- Top of the inning
- The first half of an inning, when the visiting team bats.
- Triple
- A hit on which the batter safely reaches third base.
- Triple play
- A single play that produces three outs. It is very rare and needs at least two runners on base with nobody out.
- Two-seam fastball
- A fastball gripped along the seams, so only two seams spin through the air. It is a bit slower than a four-seamer but moves more. See also: Four-seam fastball, Sinker
U
- Umpire
- An official who enforces the rules and calls balls, strikes, outs, and safes. The home plate umpire stands behind the catcher.
- Uncle Charlie
- Old slang for a curveball.
W
- Walk
- When a batter receives four balls and goes to first base. Also called a base on balls and scored as BB. See also: Intentional walk, Ball
- Walk-off
- A hit or play by the home team in the bottom of the last inning that scores the winning run and ends the game immediately.
- Warning track
- The strip of dirt or gravel in front of the outfield wall. The change in footing tells fielders they are close to the fence.
- WHIP
- Walks plus hits per inning pitched: a pitching stat showing how many baserunners a pitcher allows. Lower is better.
- Wild pitch
- A pitch so far off target that the catcher cannot handle it with ordinary effort, letting a runner move up. It is charged to the pitcher.
- Windmill
- Softball term. The standard fastpitch delivery, in which the pitcher swings the arm in a full circle before releasing the ball underhand.
FAQ
Common questions
What are the basic baseball terms?
Start with how the game is structured: inning, out, at-bat, count, ball, strike, and walk. Then learn the ways a batter reaches base (single, double, triple, home run, error, and fielder's choice) and how outs are made (strikeout, fly out, force out, and tag out). Add the field words, like infield, outfield, mound, and home plate, and you can follow almost any game.
What is an RBI?
RBI stands for run batted in. A batter earns one for each run that scores because of their plate appearance, such as on a hit, a sacrifice fly, or a walk with the bases loaded. A batter does not get an RBI when the run scores on an error or while hitting into a double play.
What is the infield fly rule?
With fewer than two outs and runners on first and second, or the bases loaded, the umpire can declare a fair pop-up that an infielder can catch with ordinary effort an automatic out. Runners may still advance at their own risk. The rule keeps fielders from letting the ball drop on purpose to turn an easy double play.
What do the position numbers mean in baseball?
Each fielding position has a number used in scorekeeping: pitcher 1, catcher 2, first base 3, second base 4, third base 5, shortstop 6, left field 7, center field 8, and right field 9. That is why a double play from shortstop to second to first is written 6-4-3. Slowpitch softball often adds a tenth fielder, sometimes numbered 10.
What is a balk?
A balk is an illegal motion by the pitcher while runners are on base, such as starting the delivery and stopping, or pretending to throw to a base without stepping toward it. The penalty is that every runner moves up one base. Softball has no balk; similar mistakes are called illegal pitches.
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