Source : Webster's Revised Unabridged Dictionary (1913)

Barbette \Bar*bette"\, n. [F. Cf. {Barbet}.] (Fort.)
   A mound of earth or a platform in a fortification, on which
   guns are mounted to fire over the parapet.

   {En barbette}, {In barbette}, said of guns when they are
      elevated so as to fire over the top of a parapet, and not
      through embrasures.

   {Barbette gun}, or {Barbette battery}, a single gun, or a
      number of guns, mounted in barbette, or partially
      protected by a parapet or turret.

   {Barbette carriage}, a gun carriage which elevates guns
      sufficiently to be in barbette. [See Illust. of
      {Casemate}.]

Source : WordNet®

barbette
     n : (formerly) a mound of earth inside a fort from which heavy
         gun can be fired over the parapet