Chapter Citharistic to Clack of C by Webster's Dictionary (1913 Edition)

2. To utter words rapidly and continually, or with abruptness; to let the tongue run.

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.]

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.