The Collaborative International Dictionary of English v.0.48:

Idealism \I*de"al*ism\, n. [Cf. F. id['e]alisme.]
   1. The quality or state of being ideal.
      [1913 Webster]

   2. Conception of the ideal; imagery.
      [1913 Webster]

   3. (Philos.) The system or theory that denies the existence
      of material bodies, and teaches that we have no rational
      grounds to believe in the reality of anything but ideas
      and their relations.
      [1913 Webster]

   4. The practice or habit of giving or attributing ideal form
      or character to things; treatment of things in art or
      literature according to ideal standards or patterns; --
      opposed to realism.
      [Webster 1913 Suppl.]

   5. a belief in the feasibility of the implementation of ideal
      principles and noble goals, and the practice or habit of
      pursuing such goals; -- opposed to realism and
      cynicism.
      [PJC]

The Collaborative International Dictionary of English v.0.48:

Maya \Ma"ya\ (m[aum]"y[aum]), n.
   1. (Hindu Philos.) The name (in Vedantic philosphy) for the
      doctrine of the unreality of matter, called, in English,
      idealism; hence, nothingness; vanity; illusion.
      [1913 Webster]

   2. (Hindu Philos.) the Hindu goddess personifying the power
      that creates phenomena. --[RHUD]
      [PJC]

   3. (Hindu Philos.) the power to produce illusions. --[RHUD]
      [PJC]

WordNet (r) 3.0 (2006):

idealism
    n 1: (philosophy) the philosophical theory that ideas are the
         only reality
    2: impracticality by virtue of thinking of things in their ideal
       form rather than as they really are
    3: elevated ideals or conduct; the quality of believing that
       ideals should be pursued [syn: high-mindedness, idealism,
       noble-mindedness]

Moby Thesaurus II by Grady Ward, 1.0:

116 Moby Thesaurus words for "idealism":
   Berkeleianism, Geistesgeschichte, Hegelian idea, Hegelianism,
   Kantian idea, Kantianism, Neoplatonism, Platonic form,
   Platonic idea, Platonism, absolute idealism, animatism, animism,
   archetype, aspiration, autism, autistic thinking, bigheartedness,
   bigness, chivalrousness, chivalry, complex idea, dereism,
   dereistic thinking, dream, dreamery, elevation, errantry,
   eternal object, eternal universal, exaltation, exemplar,
   flight of fancy, form, formal cause, generosity, generousness,
   great heart, greatheartedness, greatness, greatness of heart,
   heroism, high goal, high-mindedness, highest category,
   history of ideas, hylozoism, ideal, ideality, idealization, ideals,
   ideate, ideatum, idee-force, imaginative exercise, immaterialism,
   impracticality, innate idea, knight-errantry, knightliness,
   largeheartedness, liberality, liberalness, loftiness, magnanimity,
   magnanimousness, materialism, metaphysical idealism, model,
   monistic idealism, nobility, noble-mindedness, nobleness,
   noosphere, noumenon, openhandedness, panpsychism, pattern, percept,
   personalism, play of fancy, princeliness, prototype, psychism,
   quixotism, quixotry, reaching high, regulative first principle,
   romance, romanticism, simple idea, solipsism, spiritualism,
   subjectivism, sublimity, subsistent form, the Absolute,
   the Absolute Idea, the Self-determined, the realized ideal,
   transcendent idea, transcendent nonempirical concept,
   transcendent universal, transcendental, universal,
   universal concept, universal essence, unpracticalness, unrealism,
   unreality, upward looking, utopianism, visionariness,
   wish fulfillment, wish-fulfillment fantasy, wishful thinking