Baseball Terms

Below are common baseball terms. Click a term to view its definition.

• Balk (Baseball) A balk is an illegal pitching action in baseball in which a pitcher deceives or misleads the baserunners — resulting in all baserunners advancing one base as a penalty.
• Bullpen The area where relief pitchers warm up before entering the game.
• Doubleheader A doubleheader is two baseball games played between the same teams in the same day — usually scheduled to make up a previously rained-out or postponed game, though some are planned at the start of the season.
• Earned Run Average Earned Run Average (ERA) is a baseball pitching statistic that measures the average number of earned runs a pitcher allows per nine innings pitched, and is the primary measure of a pitcher's effectiveness.
• Hit and Run (Baseball) The hit and run is an offensive baseball strategy in which a baserunner begins running on the pitch while the batter is obligated to swing — designed to advance the runner, open a hole in the infield, and avoid double plays.
• Batting Average Batting average is a baseball statistic that measures how often a batter gets a hit, calculated by dividing the number of hits by the number of at-bats.
• Batting Order The batting order is the sequence in which nine players are scheduled to bat throughout a baseball game, determined by the manager before each game and designed to maximize the team's run-scoring potential.
• Cleanup Hitter The cleanup hitter bats fourth in the lineup and is typically the team's most powerful run producer — positioned to drive in the runners who reached base ahead of them in the three-spot.
• Closer A closer is a relief pitcher who specializes in pitching the final inning of a game to preserve a lead — typically the team's most dominant reliever.
• Designated Hitter The designated hitter (DH) is a player who bats in place of the pitcher but does not play a defensive position, allowing teams to use a more powerful offensive player without fielding responsibilities.
• Double Play A defensive play in which two offensive players are put out as a result of continuous action.
• Error (Baseball) An error in baseball is a misplay by a fielder that allows a batter or baserunner to advance when they should have been put out, and affects earned run averages and batting statistics.
• Grand Slam (Baseball) A grand slam is a home run hit with runners on all three bases (bases loaded), scoring four runs — the maximum possible on a single play in baseball.
• Hit by Pitch A hit by pitch (HBP) in baseball occurs when a pitched ball strikes the batter's body while they are in the batter's box — awarding the batter first base and sometimes resulting in a warning or ejection for intentional plunking.
• Home Run When a batter hits the ball out of play in fair territory, scoring a run for themselves and any runners on base.
• No-Hitter A no-hitter is a rare pitching achievement where a pitcher allows no hits to the opposing team throughout a complete game of at least nine innings.
• On-Base Percentage (OBP) On-base percentage (OBP) measures how often a batter reaches base per plate appearance — counting hits, walks, and hit-by-pitches — and is considered a more complete measure of a batter's value than batting average alone.
• OPS (On-Base Plus Slugging) OPS (On-Base Plus Slugging) is a composite baseball statistic that combines a hitter's on-base percentage and slugging percentage into a single number to measure overall offensive value.
• Perfect Game A perfect game is the rarest pitching achievement in baseball, where a pitcher retires every opposing batter in order across at least nine innings without any batter reaching base for any reason.
• Pinch Hitter A pinch hitter is a substitute batter who replaces another player in the lineup, typically used in high-leverage situations to gain a tactical advantage.
• Pitch Count A pitch count is the running total of pitches thrown by a pitcher in a game or outing, used by managers and coaches to monitor workload, manage fatigue, and protect pitcher health — particularly arm health over a long season.
• Relief Pitcher A relief pitcher is any pitcher who enters the game after the starting pitcher — responsible for protecting a lead, keeping the game close, or shutting down the opposing offense in late-inning situations.
• Sacrifice Fly A sacrifice fly is a fly ball out that scores a run when a baserunner tags up and scores from third base after the catch, and does not count against the batter's batting average.
• Shutout A shutout in baseball occurs when a team's pitching staff allows zero runs throughout an entire game — if a single pitcher completes the game without allowing a run, it is recorded as an individual shutout for that pitcher.
• Spring Training The preseason practice and exhibition period where MLB teams prepare players for the regular season through workouts, drills, and non-counting games.
• Stolen Base When a baserunner advances to the next base while the pitcher is delivering the ball to home plate.
• Strikeout When a batter accumulates three strikes during their at-bat and is out.
• Trade Deadline The MLB trade deadline is the annual cutoff date — July 31 — after which teams can no longer trade players with other clubs for the remainder of the season.
• Walk (Baseball) A walk in baseball (base on balls) occurs when a pitcher throws four balls to a batter, who is then awarded first base, and is a key measure of a pitcher's control and a batter's plate discipline.
• Walk-Off A walk-off is any play that ends a baseball game in the home team's favor, causing the fielding team to immediately "walk off" the field.
• WAR (Wins Above Replacement) WAR (Wins Above Replacement) is an all-in-one baseball statistic that estimates how many wins a player contributes to their team compared to a freely available replacement-level player — the most comprehensive single metric for evaluating player value.
• WHIP WHIP (Walks plus Hits per Inning Pitched) is a pitching statistic that measures how many baserunners a pitcher allows per inning — the lower the WHIP, the more dominant the performance.
• Wild Pitch A wild pitch is a pitched ball so far out of the strike zone that the catcher cannot control it, allowing baserunners to advance or a batter to reach base on a third strike.