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.

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.

Source: Webster's Revised Unabridged Dictionary (1913)
 

Clack \Clack\, v. i. [imp. & p. p. Clacked; p. pr. & vb. n. Clacking.]

[Prob. of imitative origin; cf. F. claquer to clap, crack, D. klakken, MHG. klac crack, Ir. clagaim I make a noise, ring. Cf. Clack, n., Clatter, Click.]

1. To make a sudden, sharp noise, or a succesion of such noises, as by striking an object, or by collision of parts; to rattle; to click.

We heard Mr.Hodson's whip clacking on the ahoulders of the poor little wretches. --Thackeray.

Source: Webster's Revised Unabridged Dictionary (1913)
 

Clack \Clack\, v. t.

1. To cause to make a sudden, sharp noise, or succession of noises; to click.

2. To utter rapidly and inconsiderately. --Feltham.

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

Source: Webster's Revised Unabridged Dictionary (1913)