Definition of tick tack:
(n) :
(onomatopoeia) The sound of repeated tapping, knocking, or clicking.
(n) :
(countable) A device used to tap on a window or door from a distance.
(n) :
(UK, uncountable) 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.]