capricious

adjective

1. subject to, led by, or indicative of a sudden, odd notion or unpredictable change; erratic: He’s such a capricious boss I never know how he’ll react.
2. Obsolete. fanciful or witty.

adjective

1. characterized by or liable to sudden unpredictable changes in attitude or behaviour; impulsive; fickle

adj.

1590s, from French capricieux “whimsical” (16c.), from Italian capriccioso, from capriccio (see caprice). Related: Capriciously; capriciousness.