clack

from The American Heritage® Dictionary of the English Language, 5th Edition.

• intransitive verb To make an abrupt, sharp sound, as in the collision of two hard surfaces.
• intransitive verb To chatter thoughtlessly or at length.
• intransitive verb To cackle or cluck, as a hen.
• intransitive verb To cause to make an abrupt, sharp sound.
• noun A clacking sound.
• noun Something that makes a clacking sound.
• noun Thoughtless, prolonged talk; chatter.

from The Century Dictionary.

• To make a quick sharp noise, or a succession of sharp sounds, as by striking or cracking; crack; rattle; snap.
• To utter sounds or words rapidly and continually, or with sharpness and abruptness; let the tongue run or rattle.
• To cause to make a sharp, short, snapping sound; rattle; clap: as, to clack two pieces of wood together.
• To speak without thought; rattle out.
• noun A sharp, repeated, rattling sound; clatter: as, the clack of a mill.
• noun In a grist-mill: That part of the mill that strikes the hopper, to move or shake it, for discharging its contents.
• noun A bell that rings when more corn is required to be put in the hopper.
• noun A valve of a pump.
• noun A ball-valve connected with the boiler of a locomotive. See ball-ralve and clack-box, 2.
• noun A kind of small windmill with a clapper, set on the top of a pole to frighten away birds. Also called clack-mill, and formerly clacket.
• noun Continual talk; prattle; gossip; tattle.
• To cluck or cackle, as a hen.

from the GNU version of the Collaborative International Dictionary of English.

• intransitive verb 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.
• intransitive verb To utter words rapidly and continually, or with abruptness; to let the tongue run.
• transitive verb To cause to make a sudden, sharp noise, or succession of noises; to click.
• transitive verb To utter rapidly and inconsiderately.
• transitive verb [Eng.] to cut off the sheep's mark, in order to make the wool weigh less and thus yield less duty.
• noun A sharp, abrupt noise, or succession of noises, made by striking an object.
• noun Anything that causes a clacking noise, as the clapper of a mill, or a clack valve.
• noun Continual or importunate talk; prattle; prating.
• noun (Mach.) the box or chamber in which a clack valve works.
• noun a dish with a movable lid, formerly carried by beggars, who clacked the lid to attract notice.
• noun (Mining) removable cover of the opening through which access is had to a pump valve.
• noun (Mach.) a valve; esp. one hinged at one edge, which, when raised from its seat, falls with a clacking sound.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun an abrupt, sharp sound, especially one made by two hard objects colliding repetitively; a clatter; in sound, midway between a click and a clunk
• noun Anything that causes a clacking noise, such as the clapper of a mill, or a clack valve.
• noun chatter; prattle
• verb to make such a sound
• verb to chatter or babble

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• verb speak (about unimportant matters) rapidly and incessantly
• noun a sharp abrupt noise as if two objects hit together; may be repeated
• noun a simple valve with a hinge on one side; allows fluid to flow in only one direction
• verb make a rattling sound
• verb make a clucking sounds, characteristic of hens