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.
South.
Clack box(Mach.), the box or chamber in which a clack valve works. — 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 sound.