The Collaborative International Dictionary of English v.0.48:

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.
      [1913 Webster]

   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.
      [1913 Webster]

   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.
      [1913 Webster]

WordNet (r) 3.0 (2006):

theurgy
    n 1: the effect of supernatural or divine intervention in human
         affairs
    2: white magic performed with the help of beneficent spirits (as
       formerly practiced by Neoplatonists)

Moby Thesaurus II by Grady Ward, 1.0:

36 Moby Thesaurus words for "theurgy":
   alchemy, bewitchery, charm, divination, enchantment, fetishism,
   glamour, gramarye, hoodoo, juju, jujuism, magic, natural magic,
   necromancy, obeah, rune, shamanism, sorcery, sortilege, spell,
   spellbinding, spellcasting, sympathetic magic, thaumaturgia,
   thaumaturgics, thaumaturgism, thaumaturgy, vampirism, voodoo,
   voodooism, wanga, white magic, witchcraft, witchery, witchwork,
   wizardry