Source : Webster's Revised Unabridged Dictionary (1913)

Fickleness \Fic"kle*ness\, n.
   The quality of being fickle; instability; inconsonancy.
   --Shak.

Source : WordNet®

fickleness
     n : unfaithfulness by virtue of being unreliable or treacherous
         [syn: {faithlessness}, {falseness}, {inconstancy}]