1) Repetitive clicking sound 2) Sign 3) Signal 4) Signaling 
• (n.) A kind of backgammon played both with men and pegs; tricktrack. • (adv.) With a ticking noise, like that of a watch. • (n.) A noise like that made by a clock or a watch.
Tick'tack` adverb With a ticking noise, like that of a watch. Tick'tack` noun [ See Tick to beat, to pat, and (for sense 2) confer Tricktrack .] 1. A noise like that made by a clock or a watch. 2. A kind of backgammon played both with men and pegs; tricktrack. « A game at ticktack with words.» Milton. 
[n] - (British) system of signalling by hand signs used by bookmakers at racetracks
noun system of signalling by hand signs used by bookmakers at racetracks