Definition of illegal

Anything that causes a foul according to the rules of a game.

24 Random Essential Billiards Terms

The point in match play where both players (or teams) need only one more game (frame) victory to win the match or race.
A ball positioned near a pocket so that a particularly positioned object ball shot at that pocket will likely go in off it, even if aimed so imperfectly that if the warrior was absent, the shot would likely result in a miss. Usually arises when a ball is being banked to a pocket.
A phrase used in snooker to describe the scenario whereby there are not enough available points on the table to level the scores for the frame, therefore the trailing player needs his/her opponent to foul in order to be able to make up the deficit. The name comes from the fact that this would normally have to be achieved by placing the leading player in foul-prone situations such as difficult snookers.
The placement of the balls, especially the cue ball, relative to the next planned shot. Also known as shape.
A Baulk line is line drawn across the table 29 inches from the bottom cushion and parallel to that cushion.
A pocket; usually used in disgust when describing a scratch (e.g., "the cue ball's gone down the sewer").
When the contact between the cue ball and object ball is dead center.
A pool table where two shims have been placed on the sides of each pocket (in the jaws beneath the cloth), making the pockets "tighter" (smaller). Such tables are "tougher" than unshimmed or single-shimmed tables.
Also lows, low, low ones. In eight-ball, to be shooting the solid suit (group) of balls (1 through 7); "you're low, remember", "you're low balls" or "I've got the lows." Compare solids, reds, little, spots, dots, unders; contrast high.
British term referring to the base or metaphorical "feet" of a ball that rattles in the jaws of a pocket before eventually dropping. Usually said of an object ball for which the intention was to pot it.
Accidentally causing the cue ball or any object ball to leave the table. It is normally a foul.
To determine the order of play, players (representing only themselves, or teams) each simultaneously shoot a ball from the kitchen (or in British games, from the baulk line) to the end rail and back toward the bottom rail. Whichever shooter's ball comes to rest closest to the bottom rail gets to choose who breaks the rack. It is permissible but not required for the lagged ball to touch or rebound from the bottom rail, but not to touch the side rails. Lagging is usually a two-party activity, though there are games such as cutthroat in which three players might lag. In the case of a tie, the tying shooters re-lag. The lag is most often used in tournament play or other competitions. In hard-break games like nine-ball and eight-ball the winner of the lag would normally take the break, while in soft-break games like straight pool would likely require the loser of the lag to break, since breaking would be a disadvantage.
When a ball is in firm contact with a cushion or another ball.
Also known as back spin, a type of spin applied to the cue ball by hitting it below its equator, causing it to spin backwards even as it slides forward on the cloth. Back spin slows the cue ball down, reduces its travel, and narrows both the carom angle after contact with an object ball, and angle of reflection off a cushion. There are several variant terms for this, including "bottom" and "bottom spin" in the US and "screw" in the UK. Draw is thought to be the first spin technique understood by billiards players prior to the introduction of leather tips, and was in use by the 1790s.
This is the red colored object ball in carom games.
In snooker, any of the 15 balls worth 1 point each that can be potted in any order. During the course of a break a player must first pot a red followed by a colour, and then a red and colour, etc., until the reds run out and then the re-spotted six colours must be cleared in their order. Potting more than one red in a single shot is not a foul - the player simply gets a point for each red potted.
In blackball, one of two groups of seven object balls that must be potted before the black. Reds are spotted before yellows, if balls from both group must be spotted at the same time. Compare stripes; contrast yellow ball.
In carom billiards, the object ball that is neither player's cue ball.
This is to watch a match with such intensity that there is worry, usually because of a wager on the game.
When the cue ball is tucked behind the corner of a pocket, therefore not allowing a direct shot at the object ball.
A two-piece cue constructed to resemble a house cue, with a near-invisible wood-to-wood joint. The subterfuge often enables a hustler to temporarily fool unsuspecting fish into thinking that he or she is an unskilled banger with no regard for finesse or equipment quality. Many league players also use cheap but solid sneaky petes as their break cues.
A game that basically cannot be lost based on disparity of skill levels; "this game is a lock for him."
Also straight eight-ball. Same as bar pool. Not to be confused with the games of straight pool or straight rail.
Also lady's aid or girly stick. A denigrating term for the mechanical bridge.
(noun) An opening in a table, cut partly into the bed and partly into the rails and their cushions, into which balls are shot (pocketed or potted).
(verb) Send a ball into a pocket, usually intentionally.
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.
In snooker, the highest-value colour ball on the table, being worth seven points. In some (especially American) snooker ball sets it is numbered "7" on its surface.
The black ball (usually numbered "8") in the eight-ball variant game blackball (and its variants); also the common British term for the slightly larger but otherwise identical 8 ball in a kelly pool set (a.k.a. American or WPA pool set).