concessin
Is unscrewing your playing cue really a concession?
Taking apart one's cue while an opponent is shooting has long been a tool of the hustler.
The idea is to give the shooter the impression that the person taking apart his cue has conceded. Often times, the shooter may then put his cue on the table perhaps moving balls, and the hustler will cry foul. Or the shooter may just miss the next shot thinking the game was already over, whereupon the hustler will put his or her cue back together and win the game. No different from a players saying I quit, and then changing his mind after his opponent misses.
It became an actual rule when tournament players began to use this tactic in competition many years ago.