The Collaborative International Dictionary of English v.0.48:

Quixotic \Quix*ot"ic\ (kw[i^]ks*[o^]t"[i^]k), a.
   1. Like Don Quixote; romantic to extravagance; prone to
      pursue unrealizable goals; absurdly chivalric; apt to be
      deluded. See also quixotism. "Feats of quixotic
      gallantry." --Prescott.
      [1913 Webster]

   2. Like the deeds of Don Quixote; ridiculously impractical;
      unachievable; extravagantly romantic; doomed to failure;
      as, a quixotic quest.
      [PJC]

            The word "quixotic" . . . has entered the common
            language, with the meaning "hopelessly naive and
            idealistic," "ridiculously impractical," "doomed to
            fail." That this epithet can be used now in an
            exclusively pejorative sense not only shows that we
            have ceased to read Cervantes and to understand his
            character, but more fundamentally it reveals that
            our culture has drifted away from its spiritual
            roots.                                --Simon Leys
                                                  (N. Y. Review
                                                  of Books, June
                                                  11, 1998, p.
                                                  35)
      [PJC]

WordNet (r) 3.0 (2006):

quixotic
    adj 1: not sensible about practical matters; idealistic and
           unrealistic; "as quixotic as a restoration of medieval
           knighthood"; "a romantic disregard for money"; "a wild-
           eyed dream of a world state" [syn: quixotic,
           romantic, wild-eyed]

Moby Thesaurus II by Grady Ward, 1.0:

35 Moby Thesaurus words for "quixotic":
   absurd, airy, autistic, chimerical, dereistic, dreamlike, dreamy,
   fanciful, fantastic, foolhardy, idealistic, impracticable,
   impractical, in the clouds, mad, optimistic, otherworldly, poetic,
   preposterous, rash, reckless, ridiculous, romancing, romantic,
   romanticized, starry-eyed, storybook, transcendental, transmundane,
   unpractical, unrealistic, unrealizable, visionary, wild,
   wish-fulfilling



The Devil's Dictionary (1881-1906):

QUIXOTIC, adj.  Absurdly chivalric, like Don Quixote.  An insight into
the beauty and excellence of this incomparable adjective is unhappily
denied to him who has the misfortune to know that the gentleman's name
is pronounced Ke-ho-tay.

    When ignorance from out of our lives can banish
    Philology, 'tis folly to know Spanish.
                                                            Juan Smith