The Collaborative International Dictionary of English v.0.48:

autism \autism\ n.
   1. (Med.) a mental disorder characterized by inability to
      engage in normal social interactions and intense
      self-absorption, and usually accompanied by other symptoms
      such as language dysfunctions and repetitive behavior.

   Note: autism usually manifests itself at an early age
         [PJC]

   2. behavior showing an abnormal level of absorption with
      one's own thoughts and disregard for external realities.
      [PJC]

WordNet (r) 3.0 (2006):

autism
    n 1: (psychiatry) an abnormal absorption with the self; marked
         by communication disorders and short attention span and
         inability to treat others as people

Moby Thesaurus II by Grady Ward, 1.0:

172 Moby Thesaurus words for "autism":
   acquisitiveness, airy nothing, alienation, anesthesia,
   autistic thinking, avoidance mechanism, bashfulness,
   blame-shifting, bubble, careerism, catatonia, chill, chilliness,
   chimera, cold blood, cold heart, coldheartedness, coldness,
   compensation, coolness, daydream, deadpan, deception,
   decompensation, defense mechanism, deluded belief, delusion,
   dereism, dereistic thinking, dispassion, dispassionateness,
   displacement, dissociability, dissociation, dream, dream vision,
   dreamery, dreamland, dreamworld, dullness, ego trip, egotism,
   emotional deadness, emotional insulation, emotionlessness, escape,
   escape into fantasy, escape mechanism, escapism, false belief,
   fantasizing, fantasy, flight, flight of fancy, frigidity,
   frostiness, graspingness, greed, heartlessness, iciness, ideal,
   idealism, ideality, idealization, ignis fatuus, illusion,
   imaginative exercise, immovability, impassibility, impassiveness,
   impassivity, impracticality, incompatibility, individualism,
   inexcitability, insociability, interest, isolation, lack of affect,
   lack of feeling, lack of touch, misbelief, misconception,
   mopishness, moroseness, narcissism, negativism, objectivity,
   obtuseness, overcompensation, passionlessness, personal aims,
   personal ambition, personal desires, personalism, pipe dream,
   play of fancy, poker face, possessiveness, privatism, projection,
   psychotaxis, quixotism, quixotry, rationalization, remoteness,
   resistance, romance, romanticism, self-absorption, self-admiration,
   self-advancement, self-centeredness, self-consideration,
   self-containment, self-deceit, self-deception, self-delusion,
   self-devotion, self-esteem, self-indulgence, self-interest,
   self-interestedness, self-jealousy, self-occupation, self-pleasing,
   self-seeking, self-serving, self-solicitude, self-sufficiency,
   selfishness, selfism, social incompatibility,
   sociological adjustive reactions, soullessness, spiritlessness,
   straight face, sublimation, substitution, sullenness, trick, trip,
   uncommunicativeness, uncompanionability, uncongeniality,
   unemotionalism, unexcitability, unfeeling, unfeelingness,
   unfriendliness, ungeniality, ungregariousness, unimpressibility,
   unimpressionableness, unpassionateness, unpracticalness, unrealism,
   unreality, unresponsiveness, unsociability, unsociableness,
   unsusceptibility, unsympatheticness, untouchability, utopianism,
   vapor, visionariness, wish fulfillment, wish-fulfillment fantasy,
   wishful thinking, withdrawal, wrong impression