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

\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\, 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.