The Collaborative International Dictionary of English v.0.48:

Unreality \Un`re*al"i*ty\, n.
   The quality or state of being unreal; want of reality.
   [1913 Webster]

WordNet (r) 3.0 (2006):

unreality
    n 1: the quality possessed by something that is unreal [ant:
         reality]
    2: the state of being insubstantial or imaginary; not existing
       objectively or in fact [syn: unreality, irreality] [ant:
       realism, reality, realness]

Moby Thesaurus II by Grady Ward, 1.0:

89 Moby Thesaurus words for "unreality":
   Prospero, absence, airiness, appearance, autism, autistic thinking,
   bodilessness, delusiveness, deprivation, dereism,
   dereistic thinking, dreamery, emptiness, ethereality,
   fallaciousness, false appearance, false light, false show,
   falseness, flight of fancy, flimsiness, ideal, idealism, ideality,
   idealization, illusionism, illusionist, illusiveness,
   imaginative exercise, immateriality, impalpability,
   imponderability, impracticality, incorporeality, insubstantiality,
   intangibility, magic, magic act, magic show, magician, mistiness,
   negation, negativeness, negativity, nihility, nonbeing, nonentity,
   nonexistence, nonoccurrence, nonreality, nonsubsistence, not-being,
   nothingness, nullity, play of fancy, prestidigitation, quixotism,
   quixotry, romance, romanticism, seeming, semblance, show,
   simulacrum, sleight of hand, sorcerer, sorcery,
   specious appearance, subtility, subtlety, tenuity, tenuousness,
   unactuality, unconcreteness, unpracticalness, unrealism,
   unsolidity, unsubstantiality, unsubstantialness, utopianism,
   vacancy, vacuity, vacuum, vagueness, visionariness, void,
   wish fulfillment, wish-fulfillment fantasy, wishful thinking