Clack

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.
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.