The following is an alphabetical list of unofficial terms, phrases, and other jargon used in baseball, and explanations of their meanings. See also baseball slang for slang in general usage that originated in baseball.

;1-1 (i.e., "one and one"), also, 0-1, 1-0, 1-2, 2-1, 2-2, 3-2

Instances of the "pitch count," the number of balls and strikes currently totaled for the batter.
;battery
The pitcher and catcher.
;beanball
A pitch intentionally thrown to hit the batter.
;bottom of the inning
The second half of an inning, during which the home team bats.
;brush-back
A pitch intentionally thrown close to a batter to intimidate or misdirect. Also chin-music.
;can of corn
An easily-caught fly ball.
;chase after
Swinging at a pitch well outside of the strike zone.
;check the runner
When the pitcher looks in the direction of a runner on base, and thereby causes him to not take as large of a lead as he would otherwise have taken.
;cleanup
The fourth batter for a team, usually a power hitter. The idea is to get some runners on base for the "cleanup" hitter to drive home.
;closer
A relief pitcher who is consistently used to get the final outs in games. Closers are often among the most overpowering pitchers.
;dinger
Home run. Also homer, round-tripper. See more nicknames in the article home run.
;down the line
On the field near the foul lines, often used to describe the location of batted balls.
;down the middle
Over the middle portion of home plate, used to describe the location of pitches.
;drop off the table
When a pitched ball (e.g., a curveball) breaks extremely sharply.
;high and tight
High, or above the strike zone, and close to the batter, used to describe the location of pitches.
;hitting for the cycle
Hit a single, double, triple and home run in the same game, not necessarily in that order.
;hot corner
The third base fielding position, so called because many batted balls arrive very quickly to the position.
;in the hole
On the infield at a location nearly exactly between fielders, used to describe the location of batted balls.
;K
Strikeout. A backwards K is sometimes used to denote a strikeout looking and forwards to indicate a strikeout swinging.
;lead off (batting order)
The player who is first in the batting order for a given team.
;lead off (base running)
When a base runner steps off of the base in order to reduce the distance to the next base, before a pitch is thrown.
;load the bases
When base runners are caused to exist on all bases (first, second, and third base).
;outside corner
Over the edge of home plate away from the batter, used to describe the location of pitches.
;pitch out
A pitch that is so far outside that it can't be hit. The catcher catches the pitch standing to allow a quick throw to try picking off a runner.
;safety squeeze
A squeeze play in which the runner on third waits for the batter to lay down a successful bunt before breaking for home. Contrast this with the suicide squeeze.
;setup man
A relief pitcher who is consistently used immediately before the closer.
;seventh-inning stretch
The period between the top and bottom of the seventh inning, when the fans present traditionally stand up to stretch their legs. In recent years, a sing-along of the song "Take Me Out to the Ball Game" has become part of this tradition, a practice most associated with Chicago broadcaster Harry Caray.
;shoestring catch
When a fielder, usually an outfielder, catches a ball just before it hits the ground, and remains running while doing so.
;slice foul
When a fly ball or line drive starts out over fair territory, then curves into foul territory due to aerodynamic force caused by spinning of the ball, imparted by the bat.
;sophomore jinx
The tendency for players to follow a good rookie season with a less-spectacular one. (This term is used outside the realm of baseball as well.) Two of the most notorious examples are Joe Charboneau and Mark Fidrych.
;squeeze play
A tactic used to attempt to score a runner from third on a bunt. There are two types of squeeze plays: suicide squeeze and safety squeeze.
;suicide squeeze
A squeeze play in which the runner on third breaks for home on the pitch, so that, if the batter does not lay down a bunt, then the runner is an easy out. Contrast this with the safety squeeze.
;Texas Leaguer
A weakly hit fly ball that drops in for a single.
;top of the inning
The first half of an inning, during which the visiting team bats.
;up the middle
On the field very close to second base, used to describe the location of batted balls.
;walkoff home run
A game-ending home run. The walkoff derives from the fact that the victims of such a hit will often walk off the field, seemingly in disgust or despair.