Source : Webster's Revised Unabridged Dictionary (1913)

Exorcism \Ex"or*cism\ (-s[i^]z'm), n. [L. exorcismus, Gr.
   'exorkizmo`s; cf. F. exorcisme.]
   1. The act of exorcising; the driving out of evil spirits
      from persons or places by conjuration; also, the form of
      conjuration used.

   2. Conjuration for raising spirits. [R.] --Shak.

Source : WordNet®

exorcism
     n : freeing from evil spirits [syn: {dispossession}]