vb. To make a sudden, sharp noise, or a succession of such noises, as by striking an object, or by collision of parts; to rattle; to click. To utter words rapidly and continually, or with abruptness; to let the tongue run.
- vb. To cause to make a sudden, sharp noise, or succession of noises; to click. To utter rapidly and inconsiderately. To clack wool, to cut off the sheep's mark, in order to make the wool weigh less and thus yield less duty.
- n. 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. Continual or importunate talk; prattle; prating.
- 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.