Merriam-Webster Collegiate Dictionary - caprice

 noun  Etymology: French, from Italian capriccio ~, shudder, perhaps from capo head (from Latin caput) + riccio hedgehog, from Latin ericius — more at head, urchin  Date: 1667  1.  a. a sudden, impulsive, and seemingly unmotivated notion or action  b. a sudden usually unpredictable condition, change, or series of changes the ~s of the weather  2. a disposition to do things impulsively  3. capriccio 3 Synonyms:  ~, whim, vagary, crotchet mean an irrational or unpredictable idea or desire. ~ stresses lack of apparent motivation and suggests willfulness by sheer ~ she quit her job. whim implies a fantastic, capricious turn of mind or inclination an odd antique that was bought on a whim. vagary stresses the erratic, irresponsible character of the notion or desire recently he had been prone to strange vagaries. crotchet implies an eccentric opinion or preference a serious scientist equally known for his bizarre crotchets.