caprice
ca.price \k*-'pre-s\ n [F, fr. It capriccio, lit., head with hair standing on end, shudder, fr.]capo head (fr. L caput) + riccio hedgehog, fr. L ericius 1: a sudden unpredictable turn or change; esp : WHIM 2: a disposition to change one's mind impulsively 3: CAPRICCIO mean an irrational or fanciful notion. CAPRICE emphasizes lack of evident motivation and suggests willfulness; FREAK suggests an impulsive, causeless change of mind; WHIM stresses the unaccountability or quaintness of a notion or desire; VAGARY suggests the erratic, extravagant, or irresponsible character of a notion or impulse, CROTCHET implies a perversely heretical or eccentric preference esp. on a trivial matter SYN syn CAPRICE, FREAK, WHIM, VAGARY, CROTCHET
Webster's English Dictionary