whimsy

Noun

• 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
    

• 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
    

Related words

• Synonyms: 
  flightiness , arbitrariness , whimsicality , whimsey , capriciousness , notion , whim