The Collaborative International Dictionary of English v.0.48:

Chimerical \Chi*mer"ic*al\, a.
   Merely imaginary; fanciful; fantastic; wildly or vainly
   conceived; having, or capable of having, no existence except
   in thought; as, chimerical projects.

   Syn: Imaginary; fanciful; fantastic; wild; unfounded; vain;
        deceitful; delusive.
        [1913 Webster]

WordNet (r) 3.0 (2006):

chimerical
    adj 1: being or relating to or like a chimera; "his Utopia is
           not as chimeric commonwealth but a practical improvement
           on what already exists"- Douglas Bush [syn: chimeric,
           chimerical, chimeral]
    2: produced by a wildly fanciful imagination; "his Utopia is not
       a chimerical commonwealth but a practical improvement on what
       already exists"- Douglas Bush