Source : Webster's Revised Unabridged Dictionary (1913)

Apostatize \A*pos"ta*tize\, v. i. [imp. & p. p. {Apostatized};
   p. pr. & vb. n. {Apostatizing}.] [LL. apostatizare.]
   To renounce totally a religious belief once professed; to
   forsake one's church, the faith or principles once held, or
   the party to which one has previously adhered.

         He apostatized from his old faith in facts, took to
         believing in ?emblances.                 --Carlyle.