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

Used when describing perfect cue ball position play.
Side spin on the cue ball that causes it to unnaturally roll off a cushion (contacted at an angle) against rather than with the ball's momentum and direction of travel. If angling into a cushion that is on the right, then reverse english would be right english, and vice versa. The angle of deflection will be steeper (narrower) than if no english were applied. The opposite of running english, which has effects other than simply the opposites of those of reverse english.
The precise center of the pool table.
To elevate the back of the cue on a shot.
Also winner. A shot in which the cue ball is used to pot another ball. In snooker and most pool games doing this is known as potting, pocketing or sinking the targeted ball. The term derives from this hazard winning the player points, while losing hazards cost the player points, in early forms of billiards. Whether the ball is an object ball or an opponent's cue ball depends upon the type of game (some have two cue balls). The move will score points in most (but not all) games in which hazards (as such) apply, such as English billiards (in which a "red winner" is the potting of the red ball and a "white winner" the potting of the opponent's cue ball, each worth a different amount of points).
Technique using different wood inlays to create picture designs on the butt of the cue.
Same as foot spot. Chiefly British today, but also an American usage ca. World War I.
When a ball is in firm contact with a cushion or another ball.
A three cushion billiards shot in which the cue ball first strikes two cushions before hitting the first object ball then hits a third cushion before hitting the second object ball. So called because the shot opens up like an umbrella after hitting the third rail. Umbrella shots may be classified as inside or outside depending on which side of the first object ball the cue ball contacts.
This is when you win a game of one pocket on your opponents break.
This is when a ball is spotted because of a foul or a handicap.
The ACS Canadian affiliate organization, the Canadian Cue Sport Association.
A situation where the cue ball is directly in front of another ball in the line of the shot such that the player is hampered by it, having to bridge over it awkwardly with the likelihood of a foul looming if the object ball is inadvertently touched.
Feel generally refers to that elusive quality that makes one cue feel special or superior to another. In essence, it is the cumulative effect of all of a cues characteristics, including weight, shaft diameter, balance, grip material, length, etc. It can vary greatly from one player to another. A cue that feels great to one player does not necessarily fell good to another.
The profile of the shaft of the cue as it as it increases in diameter from the tip to the joint. A "fast" or "slow" taper refers to how quickly the diameter increases. A "pro" taper describes a shaft that tapers rapidly from the joint size to the tip size so as to provide a long, untapered stroking area.
Also straight eight-ball. Same as bar pool. Not to be confused with the games of straight pool or straight rail.
In pool, the degree to which racked balls move apart upon impact by the cue ball as a result of a break shot.
In snooker, a shot sending the cue ball into the pack of red balls and separating them (after potting the ball-on). At least one split is usually necessary in each frame, since the original triangle of reds does not allow any balls to be potted reliably.
An imaginary line dividing the table into two equal halves lengthwise. It intersects the head string, center string and foot string at the head spot, center spot and foot spot, respectively.
A gentle tap of the cue ball with the intention of getting it as tight as possible behind another ball, in the hope of a snooker. It is most common in the game of snooker, and is illegal in many pool games, in which on every shot a ball must either be pocketed, or some ball must contact a cushion after the cue ball has contacted an object ball.
A defensive action taken when a player either has no "makeable" or "high percentage" shot or chooses to leave his opponent in a difficult situation. It is a legal shot and is not considered to be dirty pool. A safety must still conform with the rule concerning hitting the correct ball first and striking a rail afterwards. If a correct ball is accidentally pocketed while playing safe, the shooter must continue to shoot.
Two or more object balls that are touching or are close together.
This is to have control on the cue ball in your shots.
When a successful non penalized break is achieved which gives the object balls a broad spread on the table.
Principally British: In snooker, if a player wins all of the required frames in a match without conceding a frame to their opponent - for example, if a player wins a best-of-nine-frame match with a score of 5-0 - this is referred to as a "whitewash". This term is based on a similar term used in the card game of "patience" in the UK. However, it is not used in the context of a 1-0 winning scoreline in a match consisting of a single frame.