Whimsy is behaviour which is unusual, playful, and unpredictable, rather than having any serious reason or purpose behind it.
英汉词典释义
n.
与众不同的幽默感
His speech was full of whimsy.他妙语如珠。
英英词典释义
Noun
1. 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"
2. 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"