The Collaborative International Dictionary of English v.0.48:

Realism \Re"al*ism\ (r[=e]"al*[i^]z'm), n. [Cf. F. r['e]alisme.]
   1. (Philos.)
      (a) As opposed to nominalism, the doctrine that genera and
          species are real things or entities, existing
          independently of our conceptions. According to realism
          the Universal exists ante rem (Plato), or in re
          (Aristotle).
      (b) As opposed to idealism, the doctrine that in sense
          perception there is an immediate cognition of the
          external object, and our knowledge of it is not
          mediate and representative.
          [1913 Webster]

   2. (Art & Lit.) Fidelity to nature or to real life;
      representation without idealization, and making no appeal
      to the imagination; adherence to the actual fact.
      [1913 Webster]

   3. the practise of assessing facts and the probabilities of
      the consequences of actions in an objective manner;
      avoidance of unrealistic or impractical beliefs or
      efforts. Contrasted to idealism, self-deception,
      overoptimism, overimaginativeness, or visionariness.
      [PJC]

WordNet (r) 3.0 (2006):

realism
    n 1: the attribute of accepting the facts of life and favoring
         practicality and literal truth [syn: realism,
         pragmatism]
    2: the state of being actual or real; "the reality of his
       situation slowly dawned on him" [syn: reality, realness,
       realism] [ant: irreality, unreality]
    3: (philosophy) the philosophical doctrine that physical objects
       continue to exist when not perceived [syn: realism, naive
       realism]
    4: an artistic movement in 19th century France; artists and
       writers strove for detailed realistic and factual description
       [syn: naturalism, realism]
    5: (philosophy) the philosophical doctrine that abstract
       concepts exist independent of their names [syn: Platonism,
       realism]

Moby Thesaurus II by Grady Ward, 1.0:

81 Moby Thesaurus words for "realism":
   Marxism, absolute realism, animalism, artlessness, atomism,
   authenticity, behaviorism, bona fideness, commonsense realism,
   dialectical materialism, down-to-earthness, earthiness,
   earthliness, empiricism, epiphenomenalism, freedom from illusion,
   genuineness, hardheadedness, health, historical materialism,
   honesty, hylomorphism, hylotheism, hylozoism, inartificiality,
   lack of feelings, legitimacy, lifelikeness, literalism, literality,
   literalness, materialism, matter-of-factness, mechanism,
   natural realism, naturalism, naturalness, naturism, new realism,
   normalcy, normality, normalness, order, photographic realism,
   physicalism, physicism, positive philosophy, positivism,
   practical-mindedness, practicality, practicalness, pragmaticism,
   pragmatism, propriety, rationality, realness, reasonableness,
   regularity, representative realism, saneness, scientism,
   secularism, sensibleness, sincerity, sober-mindedness,
   substantialism, temporality, true-to-lifeness, truth to nature,
   unadulteration, unaffectedness, unfictitiousness, unidealism,
   unromanticalness, unsentimentality, unspeciousness, unspuriousness,
   unsyntheticness, verisimilitude, wholesomeness, worldliness



The Devil's Dictionary (1881-1906):

REALISM, n.  The art of depicting nature as it is seen by toads.  The
charm suffusing a landscape painted by a mole, or a story written by a
measuring-worm.