Source : Webster's Revised Unabridged Dictionary (1913)

Whimsey \Whim"sey\, Whimsy \Whimsy\, n.; pl. {Whimseys}or
   {Whimsies}. [See {Whim}.]
   1. A whim; a freak; a capricious notion, a fanciful or odd
      conceit. ``The whimsies of poets and painters.'' --Ray.

            Men's folly, whimsies, and inconstancy. --Swift.

            Mistaking the whimseys of a feverish brain for the
            calm revelation of truth.             --Bancroft.

   2. (Mining) A whim.

Whimsey \Whim"sey\, v. t.
   To fill with whimseys, or whims; to make fantastic; to craze.
   [R.]

         To have a man's brain whimsied with his wealth. --J.
                                                  Fletcher.

Source : WordNet®

whimsey
     n 1: an odd or fanciful or capricious idea; "the theatrical
          notion of disguise is associated with disaster in his
          stories"; "he had a whimsy about flying to the moon";
          "whimsy can be humorous to someone with time to enjoy
          it" [syn: {notion}, {whim}, {whimsy}]
     2: the trait of acting unpredictably and more from whim or
        caprice than from reason or judgment; "I despair at the
        flightiness and whimsicality of my memory" [syn: {flightiness},
         {arbitrariness}, {whimsicality}, {whimsy}, {capriciousness}]