To clack wool, to cut off the sheep's mark, in order to make the wool weigh less and thus yield less duty. [Eng.]
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.