Source : Webster's Revised Unabridged Dictionary (1913)

Trounce \Trounce\, v. t. [imp. & p. p. {Trounced}; p. pr. & vb.
   n. {Trouncing}.] [F. tronce, tronche, a stump, piece of wood.
   See {Truncheon}.]
   To punish or beat severely; to whip smartly; to flog; to
   castigate. [Colloq.]