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]

Moby Thesaurus II by Grady Ward, 1.0:

26 Moby Thesaurus words for "conjuration":
   abracadabra, charm, conjurement, escamotage, evocation,
   exorcisation, exorcism, exsufflation, hanky-panky, hocus-pocus,
   hokey-pokey, incantation, invocation, jiggery-pokery, jugglery,
   juggling, legerdemain, magic formula, magic words, monkey business,
   mumbo jumbo, open sesame, prestidigitation, rune, sleight of hand,
   trickery



Bouvier's Law Dictionary, Revised 6th Ed (1856):

CONJURATION. A swearing together. It signifies a plot, bargain, or compact
made by a number of persons under oath, to do some public harm. In times of
ignorance, this word was used to signify the personal conference which some
persons were supposed to have had with the devil, or some evil spirit, to
know any secret, or effect any purpose.