Source : Webster's Revised Unabridged Dictionary (1913)

Exorcist \Ex"or*cist\ (-s[i^]st), n. [L. exorcista, Gr.
   'exorkisth`s: cf. F. exorciste.]
   1. One who expels evil spirits by conjuration or exorcism.

            Certain of the vagabond Jews, exorcists. --Acts xix.
                                                  13.

   2. A conjurer who can raise spirits. [R.]

            Thou, like an exorcist, hast conjured up My
            mortified spirit.                     --Shak.

Source : WordNet®

exorcist
     n 1: one the minor orders in the unreformed Western Church but
          now suppressed in the Roman Catholic Church
     2: someone who practices exorcism [syn: {exorciser}]