资料来源 : Webster's Revised Unabridged Dictionary (1913)

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.

资料来源 : WordNet®

clack valve
     n : a simple valve with a hinge on one side; allows fluid to
         flow in only one direction [syn: {clack}, {clapper valve}]