likely to change your opinion or your feelings suddenly and without a good reason

She's so fickle - she's never been interested in the same man for more than a week! 她是如此变幻无常，喜欢同一个男人从未超过一星期。

The world of popular music is notoriously fickle. 流行音乐界的变幻无常是出了名的。

Fickle conditions are likely to change suddenly and without warning.

Fickle winds made sailing conditions difficult. 风向不定增加了航海的难度。