Capricious means unpredictable or whimsical.
Capricious is an adjective.
Synonyms: eccentric, wavering, unsteady, vacillating, fickle, witty, flighty, impulsive, erratic, changeable.
Antonyms: stable, steady, resolute, unchangeable, fixed, inflexible, constant, consistent, firm, invariable.
Note: A caprice is a whim or a sudden change of mind.
We enjoy Sai's capricious mind, but it makes him completely unreliable.
The state will soon learn the hazards of electing a capricious chief minister.
The weather was capricious and it was the major hurdle for the match; few minutes it was raining and the next few minutes it was hot and sunny.