Glossary

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53 essential baseball terms — searchable, filterable, and tappable from anywhere.

Starter pitching: The pitcher who begins the game; typically goes 5+ innings on a 4- or 5-day rotation.
Reliever pitching: A pitcher who enters after the starter exits — usually for an inning or two.
Closer pitching: The reliever assigned to the 9th inning of close games. Earns saves.
Bullpen pitching: The collection of relief pitchers; also the area where they warm up.
Strike Zone pitching: The vertical column over home plate from the batter's knees to mid-chest. Pitches inside it are strikes; outside are balls.
Strikeout (K) pitching: Three strikes against a batter ends his at-bat as an out.
Walk (BB) pitching: Four balls put the batter on first base. Officially Base on Balls.
Pitch Count pitching: Number of pitches thrown by a pitcher; modern starters typically exit between 90 and 110.
Save stat: A reliever's stat for finishing a win with no more than a 3-run lead (and other criteria).
Hold stat: A reliever stat for entering with a lead, recording outs, and leaving with the lead intact.
Blown Save stat: A save situation that the reliever fails to convert by allowing the tying run to score.
Hit play: A ball put in play that lets the batter reach base safely without an error.
Home Run play: A hit (usually over the fence in fair territory) that scores the batter and any runners.
RBI stat: Runs Batted In — a batter is credited when his at-bat causes a runner (or himself) to score.
At-Bat play: A plate appearance that results in something other than a walk, sacrifice, or HBP.
Pitcher fielding position: The fielder on the mound who throws each pitch. Position number 1.
Catcher fielding position: Crouches behind home plate, calls pitches, and throws out base stealers. Position 2.
First Baseman fielding position: Receives throws from infielders to retire batters at first base. Position 3.
Second Baseman fielding position: Covers the right side of second base; turns double plays. Position 4.
Shortstop fielding position: Covers between 2nd and 3rd; typically the best infield defender. Position 6.
Third Baseman fielding position: Plays the 'hot corner'; reacts to hard-hit balls down the line. Position 5.
Left Fielder fielding position: Patrols left field. Position 7.
Center Fielder fielding position: The deepest, fastest outfielder; covers the most ground. Position 8.
Right Fielder fielding position: Patrols right field; typically the strongest outfield throwing arm. Position 9.
Inning play: A unit of play with a top half (visitors bat) and bottom half (home bats); a regulation game has 9.
Out play: Three outs end a half-inning. Recorded by strikeout, fly out, ground out, force out, or tag.
Run play: Scored when a runner safely touches all four bases (1st, 2nd, 3rd, home).
Error play: A misplay by a fielder that lets a batter reach or a runner advance. Reflected as 'E' on the line score.
Double Play play: A defensive play that records two outs on a single batted ball — typically 6-4-3 or 4-6-3.
Stolen Base play: A runner advances a base while the pitcher throws to home, without the batter putting the ball in play.
Sacrifice Fly play: A fly out deep enough that a runner on third tags up and scores. Doesn't count as an at-bat.
Balk rule: An illegal motion by the pitcher with runners on base; all runners advance one base.
No-Hitter play: A complete game in which the pitcher (or staff) allows no hits. Walks are allowed.
Perfect Game play: A no-hitter with no baserunners at all — 27 up, 27 down. Rare; about once a decade.
Batting Average (AVG) stat: Hits divided by at-bats. Read as a 3-decimal '.300' figure. .300 is excellent; .250 is league-average.
ERA stat: Earned Run Average. Earned runs allowed per 9 innings. Lower is better; 3.00 is excellent.
WHIP stat: Walks + Hits per Inning Pitched. Measures baserunners allowed. 1.10 is elite.
OPS stat: On-base Plus Slugging. Sum of OBP and SLG. .800+ is good; 1.000+ is MVP-tier.
WAR stat: Wins Above Replacement. A composite stat estimating how many wins a player adds vs. a freely-available bench player.
RISP situation: Runners In Scoring Position — runners on 2nd or 3rd base. Batting averages with RISP often diverge from career marks.
Designated Hitter (DH) rule: A non-fielding batter who hits in the pitcher's spot. Universal in MLB since 2022.
Infield Fly Rule rule: With runners on 1st & 2nd (or bases loaded), fewer than 2 outs, a routine pop-up to an infielder is auto-out — prevents intentional drops to start a double play.
Pitch Clock rule: Pitcher must begin delivery within 15s (bases empty) or 18s (with runners). In effect since 2023.
ABS Challenge rule: Automated Ball-Strike challenge system, debuting MLB-wide in 2026. Each team gets 2 ball/strike challenges per game.
Ghost Runner rule: Runner placed on 2nd base to start every extra inning in the regular season. Does not apply in the postseason.
Rotisserie fantasy: Season-long fantasy format where teams are ranked 1-N in each of 10 categories at season's end. Last place gets 1 point, first gets N points. No head-to-head matchups.
H2H Categories fantasy: Head-to-head fantasy format with weekly matchups across 10 categories. You 'win' each category individually each week.
H2H Points fantasy: Head-to-head fantasy format converting every stat to a fantasy point value. Highest weekly total wins.
Snake Draft fantasy: A reverse-order draft: pick 12 in round 1 picks first in round 2. Most fantasy leagues use this.
Auction Draft fantasy: Each manager gets a $260 budget and bids on players one at a time. Total spend caps at $260 across 23 roster spots.
FAAB fantasy: Free Agent Acquisition Budget — a blind-bid system replacing traditional waiver order. Each manager gets a fixed budget for the season.
Streaming fantasy: Rotating starting pitchers in and out of your active lineup based on weekly schedule, opponent, and park to extract Wins and Ks while protecting ratios.
Two-Start Week fantasy: A pitcher with two scheduled starts in a fantasy week. Roughly double the K and W upside vs. a one-start ace.