a.

1. 想入非非的，異想天開的
   a whimsical notion

   離題的想法

   At that moment, a whimsical idea occurred to me: why don't I propose to her from outer space?

   在那個時候，我突然有個異想天開的念頭：我為什麼不從外太空向她求婚？

2. 怪誕的，古怪的
   a whimsical man

   古怪的傢伙

3. 反覆無常的

adj.

1. playfully quaint or fanciful, especially in an appealing and amusing way.
2. acting or behaving in a capricious manner.