1. fickle
an fickle friend
fickle friends/supporters/weather
She was so fickle in her politics, it was hard to pinpoint her beliefs; one week she would embrace a side, and the next week she would denounce it.
Cats are fickle creatures.
Judy is terribly fickle and often changes her boyfriends.
Her fickle moods make me go crazy!
How can you have trusted someone as fickle as Joan?
The weather is fickle.