Definition of rack (noun)

A geometric form, usually aluminum, wooden or plastic, used to assist in setting up balls in games like eight-ball, nine-ball, and snooker. The rack allows for more consistently tight grouping of balls, which is necessary for a successful break shot. In most games a triangle-shaped rack capable of holding fifteen balls can be employed, even if the game calls for racking less than a full ball set, such as in the game of nine-ball. For further information, see the Rack (billiards) main article.
In some games, refers to a single frame.

24 Random Essential Billiards Terms

A stroking technique in which a player releases his gripping hand briefly and re-grasps the cue farther back on the butt just before hitting the cue ball.
This is the way a ball rolls when impeded by something on the table or a blemish in the cloth, often times regular players will remember certain rolls and play to them.
A tournament format in which each contestant plays each of the other contestants at least once. In typical league team play, round robin format means that each member of the home team plays each member of the visiting team once. This format is used by BCAPL, VNEA and many other leagues.
Any one of numerous acts which unethical players employ to rattle or upset their opponent. Taking, making noise, and chalking your cue while your opponent is shooting are all considered sharking tactics.
This is a shot in one pocket pool where you simple aim at a cluster of balls near your opponents pocket to attempt to make something good happen out of desperation because other shots are not feasible.
A unit of scoring, in games such as snooker and straight pool with numerical scoring.
A unit of scoring, in team matches in leagues that use numerical scoring instead of simple game/frame win vs. loss ratios.
Another term for knuckle / tittie.
To play even; without a handicap. Also called heads up.
Chiefly American: The short rail at the foot of the table. Frequently used imprecisely, to mean foot cushion. Compare top rail; contrast head rail.
Actual wire or string with multiple beads strung (like an abacus) used for keeping score. Points "on the wire" are a type of handicap used, where a weaker player will be given a certain number of points before the start of the game.
This is a particular ball which lends itself to be used as a "blocker" or a "protector."
To use a particular ball as security by playing a safety or leaving it where it will act as one.
Netted or cupped pockets that do not return the balls to the foot end of the table by means of a gutter system or sloped surface beneath (they must instead be retrieved manually).
Nickname for the nine ball, usually only used when playing the game 9-Ball.
A requirement under some pocket billiards rulesets that either an object ball be pocketed, or at least four object balls be driven to contact the cushions, on the opening break shot.
The pocket chosen to house the selected ball in your called shot.
An imaginary line drawn from the desired path an object ball is to be sent (usually the center of a pocket) and the center of the object ball.
Same as duck. Derives from an easily shot ball "hanging" in the pocket.
A term used in snooker for the potting of all the balls that are racked at the beginning of the frame in a single break (run). The minimum total clearance affords 72 points (barring multiple reds being potted on a single stroke), in the pattern of red then yellow repeatedly until all reds are potted, then all of the colour balls. The maximum break is 147 (barring a foul by the opponent immediately before the break began).
Toward the foot of the table.
Chiefly American: The cushion on the foot rail. Compare top cushion; contrast head cushion.
The overall competition between two players, two pairs of players or two teams of players, usually consisting of a predetermined number of frames or games (sometimes organized into rounds).
In snooker, a situation where the scores are tied after all the balls have been potted, and the black ball is re-spotted and the first player to pot it wins. The players toss for the first shot, which must be taken with the cue ball in the D. A safety battle typically ensues, until an error allows a player to pot the black, or a fluke or a difficult pot is made.
Sometimes interchangeable with scratch, though the latter is often used only to refer to the foul of pocketing the cue ball. A violation of a particular game's rules for which a set penalty is imposed.
To play a shot with the stroke and speed that makes it easiest to pocket the object ball, even at the expense of sacrificing position.
Common slang in the US for a cheap, poorly made cue. Compare wood.