The Collaborative International Dictionary of English v.0.48:

Idealistic \I*de`al*is"tic\, a.
   Of or pertaining to idealists or their theories.
   [1913 Webster]

WordNet (r) 3.0 (2006):

idealistic
    adj 1: of or relating to the philosophical doctrine of the
           reality of ideas [syn: ideal, idealistic]
    2: of high moral or intellectual value; elevated in nature or
       style; "an exalted ideal"; "argue in terms of high-flown
       ideals"- Oliver Franks; "a noble and lofty concept"; "a grand
       purpose" [syn: exalted, elevated, sublime, grand,
       high-flown, high-minded, lofty, rarefied, rarified,
       idealistic, noble-minded]

Moby Thesaurus II by Grady Ward, 1.0:

101 Moby Thesaurus words for "idealistic":
   Berkeleian, Cyrenaic, Eleatic, Epicurean, Hegelian, Kantian,
   Megarian, Neoplatonic, Neoplatonistic, Platonic, Platonistic,
   Stoic, airy, animist, animistic, atomistic, autistic, big,
   bighearted, chivalrous, cosmotheistic, dereistic, eclectic,
   elevated, empirical, eudaemonistic, exalted, existential, generous,
   great, great of heart, greathearted, handsome, hedonic, hedonist,
   hedonistic, heroic, high, high-minded, humanist, humanistic,
   idealist, immaterialist, impractical, in the clouds,
   instrumentalist, knightly, largehearted, liberal, lofty,
   magnanimous, materialistic, mechanistic, metaphysical, monistic,
   naturalistic, noble, noble-minded, nominalist, openhanded,
   optimistic, otherworldly, panlogistical, panpsychist,
   panpsychistic, pantheistic, poetic, positivist, positivistic,
   pragmatic, pragmatist, princely, quixotic, rationalistic, realist,
   realistic, romancing, romantic, romanticized, scholastic,
   sensationalistic, solipsistic, spiritualist, spiritualistic,
   starry-eyed, storybook, sublime, syncretistic, theistic,
   transcendental, transcendentalist, transcendentalistic,
   transmundane, unpractical, unrealistic, utilitarian, visionary,
   vitalistic, voluntarist, voluntaristic, wish-fulfilling