Definition of Chalk

A style of game play in which as many players are allowed to join as the participants choose, and anyone can quit at any time. The term, most often used in the context of gambling, is borrowed from poker. The folk games three-ball and killer are usually played as open ring games, as is Kelly pool.
By extension, a multi-player game that anyone may initially join, but which has a fixed roster of competitors once it begins, is sometimes also called a ring game. Cutthroat is, by its nature, such a game. A famous regular ring game event of this sort is the Grady Mathews-hosted six-player, $3000-buy-in ring ten-ball competition at the annual Derby City Classic.
A nine-ball ring game is played by more than two players. Safeties are not allowed.

Same as side rail.

This is to win a game by pocketing enough balls before you opponent.

Either of the balls on the lateral extremities of a racked set of balls in position for a break shot; the two balls at the outside of a 15-ball rack in the back row, or the balls to the left and right of the 9 ball in nine-ball's diamond rack-shaped opening set up position. In nine-ball It is seen as a reliable sign of a good break (which is normally taken from close to either cushion in the kitchen) if the opposite wing ball is pocketed.

An imaginary line running horizontally across a billiards table from the second diamond (from the foot end of the table) on one long rail to the corresponding second diamond on the other long rail. The foot string intersects the long string at the foot spot. It is rarely drawn on the table.

Same as break.

Describing a pot played at such a pace as to just reach the pocket and drop in without hitting the back.

The Higher Education Snooker and Pool Council is a voluntary, not-for-profit organisation established to promote cue sports in institutions of higher education on the island of Ireland.

Short for left english (side), i.e. spin imparted to the cue ball by stroking it to the lefthand side of its vertical axis. Contrast right.

Same as duck. Derives from an easily shot ball "hanging" in the pocket.

Technique using different wood inlays to create picture designs on the butt of the cue.

A thin sheet of rigid material in the size and shape of a physical ball rack (e.g. a diamond for nine-ball), with holes drilled though it, which is used to make permanent divots in the cloth of the table, one at a time for each ball in the racking pattern, by placing a ball in one of the holes in the carefully placed template and tapping it sharply from above to create the cloth indentation. The holes are spaced slightly closer than the regulation ball width of 21/2 inch (57.15 mm) apart, so that when the balls settle partially into their divots, the outer sides of these indentations create ball-on-ball pressure, pushing the balls together tightly. The purpose of the template is to do away with using a physical rack, with racking instead being performed simply by placing the balls into position, and the divots aligning them into the tightest possible formation automatically. This prevents accidental loose racks, and also thwarts the possibility of cheating by carefully manipulating the ball positions while racking. The European Pocket Billiard Federation (EPBF, Europe's WPA affiliate organization) has adopted this racking technique for its professional Euro-Tour event series.

To fail to make a legal shot.

Local Bylaws are additional rules, policies, and procedures unique to an area in addition (or subtraction) to established Pool/Billiards/Snooker league rules. They are designed to cover local situations.

Same as feather (US) or snick (UK)

Chiefly British: bank shot played up and down the longer length of the table off a short rail and into a corner pocket, as opposed to the more common bank across the short length into a center pocket or corner.

The game of snooker. This is a very demanding game that isn't played as often in the U.S. as it is in other countries. The table needed is slightly larger, and there are 15 red object balls needed in addition to six color balls. After the balls are set up according to the rules, play resumes in turns with points scored as one on each red ball, and as is denoted with each other colored ball sunk. This is a challenging game that demands skill and excellent execution.
To leave the opponent (accidentally or by means of a safety) so that a certain shot on a preferred object ball cannot be played directly in a straight line by normal cueing. It most commonly means that the object ball cannot be hit, because it is hidden by another ball or, more rarely, the knuckle of a pocket (see corner-hooked). It can also refer to the potting angle or another significant point of contact on the object ball, blocking an otherwise more straightforward shot, even if an edge can be seen. A common related adjective describing a player in this situation is snookered. Also known as "to hook", for which the corresponding adjective "hooked" is also common. See also free ball.
An instance of this situation (e.g. "she's put him in a difficult snooker"). A player can choose a range of shots to get out of a snooker; usually a kick shot will be implemented but semi-massés are often preferred, and in games where it is not a foul, jump shots may be employed that often yield good results for skilled players. "Snooker" is used loosely (when used at all; "hook" is favored) in the US, but has very specific definitions and subtypes (such as the total snooker) in blackball.

In nine-ball, especially in the UK, a break shot that pots the 9 ball without fouling, in which case the player wins in one shot. See also on the break/snap.

Used with an amount to signify money added to a tournament prize fund in addition to the amount accumulated from entry fees (e.g. "$500 added").

Verb: "To Clock" To carefully note the abilities or betting inclinations of other players for future reference.

Also known as a "Dirty Defense" or "Dirty Foul". To intentionally miss a shot (that results in a foul) in order to create a position for the cue ball that makes it hard for the other player to execute their shot. Not to be confused with a "Safety", since a safety is a legal hit.

Used by itself often with "low" and "high": "that's a low-percentage shot for me", "I should really take the high-percentage one".

This is when a mistake is made in the shot and the resulting contact between balls forces you to miss the shot.

This is a handicapping method where one player gets the break, and is allowed to choose any ball afterwards to put in their pocket.