The Collaborative International Dictionary of English v.0.48:

Ticktack \Tick"tack`\, n. [See Tick to beat, to pat, and (for
   sense 2) cf. Tricktrack.]
   1. A noise like that made by a clock or a watch.
      [1913 Webster]

   2. A kind of backgammon played both with men and pegs;
      tricktrack.
      [1913 Webster]

            A game at ticktack with words.        --Milton.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Ticktack \Tick"tack`\, adv.
   With a ticking noise, like that of a watch.
   [1913 Webster]

WordNet (r) 3.0 (2006):

ticktack
    n 1: system of signalling by hand signs used by bookmakers at
         racetracks
    v 1: make a sound like a clock or a timer; "the clocks were
         ticking"; "the grandfather clock beat midnight" [syn:
         tick, ticktock, ticktack, beat]