Source : Webster's Revised Unabridged Dictionary (1913)

Decapitate \De*cap"i*tate\, v. t. [imp. & p. p. {Decapitated};
   p. pr. & vb. n. {Decapitating}.] [LL. decapitatus, p. p. of
   decapitare; L. de- + caput head. See {Chief}.]
   1. To cut off the head of; to behead.

   2. To remove summarily from office. [Colloq. U. S.]

Source : WordNet®

decapitated
     adj : having had the head cut off; "the beheaded prisoners" [syn:
           {beheaded}]