From WordNet (r) 3.0 (2006):
clack
n 1: a sharp abrupt noise as if two objects hit together; may be
repeated [syn: clack, clap]
2: a simple valve with a hinge on one side; allows fluid to flow
in only one direction [syn: clack valve, clack, clapper
valve]
v 1: make a rattling sound; "clattering dishes" [syn: clatter,
clack, brattle]
2: make a clucking sounds, characteristic of hens [syn: cluck,
click, clack]
3: speak (about unimportant matters) rapidly and incessantly
[syn: chatter, piffle, palaver, prate, tittle-
tattle, twaddle, clack, maunder, prattle, blab,
gibber, tattle, blabber, gabble]