Noun
(onomatopoeia) The sound of repeated tapping, knocking, or clicking.
(countable) A device used to tap on a window or door from a distance.
(UK, uncountable) Alternative form of tic-tac, a sign language used by bookmakers.
Alternative form of tick tack, the sound of tapping; a device to tap on a window
Alternative form of tic-tac, a sign language used by bookmakers
Source: en.wiktionary.orgtick-tack