Definition of tick-tack:
(n) :
Alternative form of tick tack, the sound of tapping; a device to tap on a window [(onomatopoeia) The sound of repeated tapping, knocking, or clicking.]
(n) :
Alternative form of tic-tac, a sign language used by bookmakers [(British) A system of sign language used by bookmakers at racecourses to communicate odds and bets; an associated group of words for each sign.]