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
;battery- The pitcher and catcher.
- A pitch intentionally thrown to hit the batter.
- The second half of an inning, during which the home team bats.
- A pitch intentionally thrown close to a batter to intimidate or misdirect. Also chin-music.
- An easily-caught fly ball.
- Swinging at a pitch well outside of the strike zone.
- 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.
- 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.
- A relief pitcher who is consistently used to get the final outs in games. Closers are often among the most overpowering pitchers.
- Home run. Also homer, round-tripper. See more nicknames in the article home run.
- On the field near the foul lines, often used to describe the location of batted balls.
- Over the middle portion of home plate, used to describe the location of pitches.
- When a pitched ball (e.g., a curveball) breaks extremely sharply.
- High, or above the strike zone, and close to the batter, used to describe the location of pitches.
- Hit a single, double, triple and home run in the same game, not necessarily in that order.
- The third base fielding position, so called because many batted balls arrive very quickly to the position.
- On the infield at a location nearly exactly between fielders, used to describe the location of batted balls.
- Strikeout. A backwards K is sometimes used to denote a strikeout looking and forwards to indicate a strikeout swinging.
- The player who is first in the batting order for a given team.
- When a base runner steps off of the base in order to reduce the distance to the next base, before a pitch is thrown.
- When base runners are caused to exist on all bases (first, second, and third base).
- Over the edge of home plate away from the batter, used to describe the location of pitches.
- 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.
- 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.
- A relief pitcher who is consistently used immediately before the closer.
- 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.
- When a fielder, usually an outfielder, catches a ball just before it hits the ground, and remains running while doing so.
- 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.
- 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.
- 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.
- 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.
- A weakly hit fly ball that drops in for a single.
- A type of elbow surgery for pitchers named after Tommy John, a pitcher and the first professional athlete to successfully undergo the operation.
- The first half of an inning, during which the visiting team bats.
- On the field very close to second base, used to describe the location of batted balls.
- 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.