capricious in WordNet English dictionary

1. determined by chance or impulse or whim rather than by necessity or reason
   "a capricious refusal"; "authoritarian rulers are frequently capricious"; "the victim of whimsical persecutions"
   capricious  impulsive  whimsical 
   
2. changeable
   "a capricious summer breeze"; "freakish weather"
   capricious  freakish