The Collaborative International Dictionary of English v.0.48:

Conjuration \Con`ju*ra"tion\, n. [L. conjuratio, cf. F.
   conjuration.]
   1. The act of calling or summoning by a sacred name, or in
      solemn manner; the act of binding by an oath; an earnest
      entreaty; adjuration.
      [1913 Webster]

            We charge you, in the name of God, take heed; . . .
            Under this conjuration speak, my lord. --Shak.
      [1913 Webster]

   2. The act or process of invoking supernatural aid by the use
      of a magical form of words; the practice of magic arts;
      incantation; enchantment.
      [1913 Webster]

            Pretended conjurations and prophecies of that event.
                                                  --Hallam.
      [1913 Webster]

   3. A league for a criminal purpose; conspiracy. [Obs.] "The
      conjuration of Catiline." --Sir T. Elyot.
      [1913 Webster]

WordNet (r) 3.0 (2006):

conjuration
    n 1: a ritual recitation of words or sounds believed to have a
         magical effect [syn: incantation, conjuration]
    2: calling up a spirit or devil [syn: conjuring,
       conjuration, conjury, invocation]
    3: an illusory feat; considered magical by naive observers [syn:
       magic trick, conjuring trick, trick, magic,
       legerdemain, conjuration, thaumaturgy, illusion,
       deception]