'Clack valve' definitions:

Definition of 'clack valve'

noun

A simple valve with a hinge on one side; allows fluid to flow in only one direction [syn: clack valve, clack, clapper valve]

From: GCIDE

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. [1913 Webster]
2. Anything that causes a clacking noise, as the clapper of a mill, or a clack valve. [1913 Webster]
3. Continual or importunate talk; prattle; prating. [1913 Webster]
Whose chief intent is to vaunt his spiritual clack. --South. [1913 Webster]
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. [1913 Webster]
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. [1913 Webster]