Source : Webster's Revised Unabridged Dictionary (1913)

Apostate \A*pos"tate\, n. [L. apostata, Gr. ?, fr. ?. See
   {Apostasy}.]
   1. One who has forsaken the faith, principles, or party, to
      which he before adhered; esp., one who has forsaken his
      religion for another; a pervert; a renegade.

   2. (R. C. Ch.) One who, after having received sacred orders,
      renounces his clerical profession.

Apostate \A*pos"tate\, a.
   Pertaining to, or characterized by, apostasy; faithless to
   moral allegiance; renegade.

         So spake the apostate angel.             --Milton.

         A wretched and apostate state.           --Steele.

Apostate \A*pos"tate\, v. i. [L. apostatare.]
   To apostatize. [Obs.]

         We are not of them which apostate from Christ. --Bp.
                                                  Hall.

Source : WordNet®

apostate
     adj : not faithful to religion or party or cause
     n : a disloyal person who betrays or deserts his cause or
         religion or political party or friend etc. [syn: {deserter},
          {renegade}, {turncoat}, {recreant}, {ratter}]