Fickle

Part of speech: adjective (a.)

Not fixed or firm; liable to change; unstable; of a changeable mind; not firm in opinion or purpose; inconstant; capricious; as, Fortune's fickle wheel. Shak. They know how fickle common lovers are. Dryden.

Synonyms: Wavering; irresolute; unsettled; vacillating; unstable; inconsonant; unsteady; variable; mutable; changeful; capricious; veering; shifting.