The Collaborative International Dictionary of English v.0.48:
Clack \Clack\, n. [Cf. F. claque a slap or smack, MHG. klac
crack, W. clec crack, gossip. See Clack, v. t.]
1. A sharp, abrupt noise, or succession of noises, made by
striking an object.
2. Anything that causes a clacking noise, as the clapper of a
mill, or a clack valve.
3. Continual or importunate talk; prattle; prating.
Whose chief intent is to vaunt his spiritual clack.
Clack box (Mach.), the box or chamber in which a clack
Clack dish, a dish with a movable lid, formerly carried by
beggars, who clacked the lid to attract notice. --Shak.
Clack door (Mining), removable cover of the opening through
which access is had to a pump valve.
Clack valve (Mach.), a valve; esp. one hinged at one edge,
which, when raised from its seat, falls with a clacking