⚾Glossary

Terms

Terms people actually search for first.

Balk Balk

An illegal pitcher motion with runners on base that deceives a runner. Common triggers: starting then stopping the delivery, failing to come set, or feinting a throw while engaged with the rubber. Penalty: all runners advance one base. Judgment-heavy, so arguments are frequent.

Base on balls Base on balls

Four pitches outside the strike zone in one plate appearance earn first base. Not a hit, but sabermetrics treats the resulting on-base event as nearly as valuable — helping OBP displace batting average. Intentional walks have been awarded by signal without pitches since 2017.

Batting average Batting average

Hits divided by at-bats; .300 means three hits in ten at-bats. For a century the headline hitter number, but it ignores walks and treats singles like home runs, so OBP and slugging have largely replaced it for evaluation — though broadcasts still lead with it.

Bullpen Bullpen

Both the warm-up area for relief pitchers and the relief corps itself. Relievers inherit games after starters leave, now often by leverage rather than inning order. Roles split into long relief, lefty specialist, setup and closer. Even adult leagues rarely see complete games, so bullpen use decides many results.

Bunt Bunt

Tapping the ball softly into the infield without a full swing. Sacrifice bunts move runners; drag or push bunts try for a hit. Analytics cut sacrifice use because the out is costly, but bunts still beat shifts and manufacture a late run.

Closer Closer

The relief pitcher who finishes games to protect a lead — usually the bullpen's best stuff, accumulating saves. Ninth-inning specialist use hardened after the 1980s, though leverage theory increasingly argues the highest-leverage outs often come in the seventh or eighth.

Cutoff man Cutoff man

The infielder who relays an outfield throw toward the infield — often the first baseman, shortstop or second baseman. One long throw home is slower and less accurate; a relay is faster and can also hold trailing runners. In adult ball, cutoff execution is the biggest preventable run-saver.

Defensive shift Defensive shift

Aligning fielders to a hitter's spray chart — classically three infielders on the pull side against lefty pull hitters. Shifts surged after 2016 and depressed batting averages until MLB restricted them in 2023: two infielders each side of second, all on the dirt at pitch.

Designated hitter Designated hitter

A tenth player who bats for the pitcher without playing defence. The American League adopted it in 1973; the National League followed in 2022, unifying the rules. It boosts offence and protects pitchers from batting injury while shrinking managerial moves like the double-switch.

Double play Double play

Two outs on one continuous play. The classic is a ground ball with a runner on first — shortstop or second baseman steps on second and throws to first (6-4-3 or 4-6-3). It ends an inning and a threat at once; hitters are charged with a GIDP.

Dropped third strike Dropped third strike

If the catcher fails to cleanly catch the third strike, the batter may run to first when first base is open or there are two outs. The pitcher still gets a strikeout; the batter can still reach, creating the oddity of four strikeouts in an inning.

Earned run average Earned run average

Earned runs allowed per nine innings: earned runs divided by innings, times nine. Errors' runs are excluded, partly isolating pitching from defence, but park size and defence quality remain unadjusted. Still the default pitcher rate stat.

Error Error

A play the official scorer judges should have been made with ordinary effort, allowing a batter or runner to advance. Subjective; runs that score only because of errors are unearned. Wide-ranging defenders often rack up errors by reaching balls others miss, so raw error totals misread defence.

Fielder's choice Fielder's choice

A fielder takes the lead runner instead of the batter, who reaches first. It counts as an at-bat without a hit, lowering batting average. Scored FC — and the item beginners most often ask about when they clearly "got on base."

Foul pole Foul pole

The yellow poles at the ends of the foul lines on the outfield fence. Despite the name, a ball that hits the pole or passes inside it is fair — a home run. Thin fair/foul calls on balls over the wall are a staple of video review.

Hit and run Hit and run

The runner breaks with the pitch while the batter must put the ball in play. Covering second opens an infield hole; a grounder through it can send the runner to third. A swing-and-miss usually means the runner is thrown out stealing.

Hit by pitch Hit by pitch

A pitch outside the zone that hits the batter awards first base. The batter must attempt to avoid it; leaning into a pitch can be ruled a ball only. Suspected intent brings warnings or ejections and can spark bench-clearing — so inside pitching always carries tension.

Hold Hold

Credited to a middle reliever who enters with a lead, keeps it, and hands the ball to another pitcher without finishing the game. Save-like criteria, no game-ending credit. Created in 1986 to record setup-man value; some leagues crown a hold champion.

Infield fly rule Infield fly rule

With runners on first and second (or bases loaded) and fewer than two outs, an ordinary catchable pop-up to the infield is an automatic out on the batter. It stops fielders from dropping the ball on purpose for a double or triple play. The ball remains live; runners may advance at their risk.

Inherited runner Inherited runner

A runner already on base when a reliever enters. If that runner scores, the earned run belongs to the pitcher who put him on, not the reliever's ERA. Judging bullpens by ERA alone therefore misses stranded-runner skill — inherited-runner scoring rate matters too.

Launch angle Launch angle

The vertical angle of the ball as it leaves the bat. After Statcast tracking spread in 2015 it became central hitting theory: with enough exit velocity, roughly 25–30 degrees maximises extra-base hits, driving the "fly-ball revolution" — and a parallel rise in strikeouts.

No-hitter No-hitter

A complete game in which a pitcher (or combination) allows no hits. Walks, errors and hit-by-pitches can still put runners on. Allowing nobody aboard at all is a perfect game. MLB sees only a handful per season; they remain rare everywhere.

Official ball Official ball

The league-approved game baseball: circumference about 9–9.25 inches, weight 5–5.25 ounces, with 108 stitches. Small changes in coefficient of restitution swing league-wide home-run rates, which is why governing bodies tightly specify the ball. Adult leagues usually mandate a brand.

On-base percentage On-base percentage

Times reaching base (hits, walks, HBP) divided by plate appearances. Because outs are a finite resource, not making outs correlates tightly with scoring — so sabermetrics elevated OBP over batting average as the first look at hitters. League average sits in the low .300s.

Pickoff Pickoff

A throw by pitcher or catcher to a base to retire or hold a runner. Actual outs are rare; the real goal is shrinking lead distance to deter steals. MLB capped disengagements at two per plate appearance from 2023 — a third failed attempt is a balk.

Pitch clock Pitch clock

A timer between pitches. MLB introduced it in 2023: 15 seconds with bases empty, 18 seconds with runners (tightened from 20 in 2024). Pitcher violations add a ball; batter delays add a strike. Average game length fell from 3:04 in 2022 to about 2:36 in 2024 — the most successful recent rules change.

Pitch framing Pitch framing

A catcher's skill at receiving borderline pitches with a still glove so umpires call strikes. Tracking data showed elite framers can save twenty-plus runs a season, shifting catcher evaluation from thrown-out steals toward receiving. Automated balls and strikes will erase much of that value.

Pitcher's mound Pitcher's mound

The raised dirt circle the pitcher throws from. Rubber to rear point of home plate is 60 feet 6 inches; the mound top sits 10 inches above the plate. It was 15 inches until lowered after the extreme pitcher year of 1968. The pivot foot must stay in contact with the rubber through the delivery.

Quality start Quality start

A start of at least six innings with three or fewer earned runs. Sportswriter John Lowe proposed it in 1985 as a steadiness measure less luck-driven than wins. Critics note 6 IP, 3 ER is a 4.50 ERA — generous by modern standards.

Run batted in Run batted in

Credit when a batter's plate appearance drives in a run — via hit, sacrifice fly, walk with bases loaded, or even certain outs. Heavily dependent on how often teammates are on base, so it is a weak pure-skill metric, yet still the traditional badge of a middle-of-the-order bat.

Sabermetrics Sabermetrics

The statistical analysis of baseball, named by Bill James in the 1970s and popularised by Moneyball's account of the early-2000s Athletics. The project prefers OBP to batting average and WAR to pitcher wins — measures that better track run contribution. Every club now runs an analytics department.

Save Save

A statistic for a reliever who finishes a game while protecting a lead under defined conditions (lead of three or fewer and at least one inning; or entering with the tying run on deck/at bat/on base; or pitching the final three innings). Official since 1969, it essentially created the closer role — a rare case of a stat reshaping tactics.

Slugging percentage Slugging percentage

Total bases divided by at-bats (single 1, double 2, triple 3, home run 4). Where batting average counts hit frequency, slugging measures how far those hits went. Added to OBP it forms OPS; league-average SLG usually sits near .400.

Squeeze play Squeeze play

A bunt designed to score the runner from third. Safety squeezes wait to see contact; suicide squeezes break with the pitch no matter what. Miss the bunt on a suicide and the runner is usually dead in a rundown — hence the name.

Stolen base Stolen base

A runner advances a base on his own during a pitch. Sabermetrics long held that success rates below about 75% cost more runs than they create, so steals fell after 2000 — then jumped again in 2023 after bigger bases and pickoff limits, to the highest MLB totals since 1987.

Strike zone Strike zone

The imaginary box over home plate from the hollow of the knee to the midpoint between shoulders and belt, varying with stance and umpire. KBO rolled out full automated balls-and-strikes in 2024; MLB plans a challenge-only robot system for 2026.

Strikeout Strikeout

Three strikes retire the batter. Swinging and looking strikeouts are scored differently (K vs ꓘ). Rising velocity plus the fly-ball approach have pushed league strikeout rates up for decades — which also means fewer balls in play.

Sweeper Sweeper

A horizontally breaking slider that spread rapidly in the 2020s. A flatter spin axis produces lateral break often exceeding 15 inches, diving away from same-handed hitters. Tracking data defined what "good" slider spin looked like, and the whole league copied it — a pitch invented by analytics.

Tag up Tag up

After a fly ball is caught, a runner retouches the original base and then advances. Leaving early risks an appeal out. A deep fly that scores a runner from third is a sacrifice fly — outfielder arm versus runner jump in a straight duel.

Walk-off Walk-off

The home team scores the winning run in the ninth or extras and the game ends immediately. A walk-off homer, walk or hit ends it on contact or the awarded base. The losing side "walks off" the field; road teams cannot walk off. It is the structural form of home-field last at-bat.

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