Source : Webster's Revised Unabridged Dictionary (1913)

Theurgy \The"ur*gy\ (th[=e]"[u^]r*j[y^]), n. [L. theurgia, Gr.
   qeoyrgi`a, fr. qeoyrgo`s doing the works of God; qeo`s God +
   'e`rgon work: cf. F. th['e]urgie. See {Theism}, and {Work}.]
   1. A divine work; a miracle; hence, magic; sorcery.

   2. A kind of magical science or art developed in Alexandria
      among the Neoplatonists, and supposed to enable man to
      influence the will of the gods by means of purification
      and other sacramental rites. --Schaff-Herzog Encyc.

   3. In later or modern magic, that species of magic in which
      effects are claimed to be produced by supernatural agency,
      in distinction from natural magic.

Source : WordNet®

theurgy
     n : magic performed with the help of beneficent spirits