1. Failure to hit any legal object ball at all with the cue ball . In most sets of rules, this is a foul like any other. However, in some variants of bar pool a table scratch while shooting for the 8 ball is a loss of game where other more minor fouls might not be, as is scratching on the 8 ball (neither result in a loss of game in professional and most amateur league rules).
2. By way of drift from the above definition, the term is also applied by many league players to the foul in more standardized rules of failing to drive a (any) ball to a cushion , or to pocket a legal object ball , after the cue ball 's initial contact with an object ball .
3. Uncommonly, and by way of entirely different derivation ("scratch off the table"), it can also mean knocking the cue ball (or more loosely, any ball) completely off the table.