fickle
adjective uk/ˈfɪk.əl/ us/ˈfɪk.əl/
disapproving（意见或感情）反复无常的，易变的
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。
（情况）变幻莫测的，不定的
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。