The Collaborative International Dictionary of English v.0.48:

Fanciful \Fan"ci*ful\, a.
   1. Full of fancy; guided by fancy, rather than by reason and
      experience; whimsical; as, a fanciful man forms visionary
      projects.
      [1913 Webster]

   2. Conceived in the fancy; not consistent with facts or
      reason; abounding in ideal qualities or figures; as, a
      fanciful scheme; a fanciful theory.
      [1913 Webster]

   3. Curiously shaped or constructed; as, she wore a fanciful
      headdress.
      [1913 Webster]

            Gather up all fancifullest shells.    --Keats.

   Syn: Imaginative; ideal; visionary; capricious; chimerical;
        whimsical; fantastical; wild.

   Usage: Fanciful, Fantastical, Visionary. We speak of
          that as fanciful which is irregular in taste and
          judgment; we speak of it as fantastical when it
          becomes grotesque and extravagant as well as
          irregular; we speak of it as visionary when it is
          wholly unfounded in the nature of things. Fanciful
          notions are the product of a heated fancy, without any
          tems are made up of oddly assorted fancies, aften of
          the most whimsical kind; visionary expectations are
          those which can never be realized in fact. --
          Fan"ci*ful*ly, adv. -Fan"ci*ful*ness, n.
          [1913 Webster]

WordNet (r) 3.0 (2006):

fanciful
    adj 1: indulging in or influenced by fancy; "a fanciful mind";
           "all the notional vagaries of childhood" [syn:
           fanciful, notional]
    2: not based on fact; unreal; "the falsehood about some fanciful
       secret treaties"- F.D.Roosevelt; "a small child's imaginary
       friends"; "to create a notional world for oneself" [syn:
       fanciful, imaginary, notional]
    3: having a curiously intricate quality; "a fanciful pattern
       with intertwined vines and flowers"

Moby Thesaurus II by Grady Ward, 1.0:

109 Moby Thesaurus words for "fanciful":
   Gothic, absurd, air-built, airy, antic, apocryphal, arbitrary,
   baroque, bizarre, brain-born, capricious, changeable, chimerical,
   cloud-built, conceptual, cranky, crotchety, curious, dream-built,
   dreamlike, ethereal, extravagant, fabulous, false, fancied,
   fancy-born, fancy-built, fancy-woven, fantasied, fantasque,
   fantastic, fatuitous, fatuous, fickle, fictional, fictitious,
   fictive, flaky, florid, freakish, gaseous, gossamery, grotesque,
   harebrained, humorsome, ideal, ideational, ideological, illusory,
   imaginary, imaginative, imagined, immaterial, impossible,
   impulsive, incomprehensible, inconceivable, inconstant, incredible,
   kinky, legendary, maggoty, make-believe, merely nominal, moody,
   motiveless, mythical, not real, notional, odd, original,
   outlandish, peculiar, petulant, phantomlike, preposterous, quirky,
   rarefied, rococo, shadowy, spirituous, subtile, subtle,
   supposititious, temperamental, tenuous, theoretical, unaccountable,
   unactual, unbelievable, unexpected, unimaginable, unreal,
   unrealistic, unreasonable, unrestrained, unsubstantial, unusual,
   vagarious, vagrant, vaporous, variable, visionary, wanton, wayward,
   whimsical, wild, windy, wrong