The Collaborative International Dictionary
Clack \Clack\, n. [Cf. F. claque a slap or smack, MHG. klac crack, W. clec crack, gossip. See Clack, v. t.]
A sharp, abrupt noise, or succession of noises, made by striking an object.
Anything that causes a clacking noise, as the clapper of a mill, or a clack valve.
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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.
Wiktionary
n. (context engineering English) A valve; especially one hinged at one edge, which, when raised from its seat, falls with a clacking sound.
WordNet
n. a simple valve with a hinge on one side; allows fluid to flow in only one direction [syn: clack, clapper valve]