Inconstant

Part of speech: adjective (a.)

Not constant; not stable or uniform; subject to change of character, appearance, opinion, inclination, or purpose, etc.; not firm; unsteady; fickle; changeable; variable; -- said of persons or things; as, inconstant in love or friendship. "The inconstant moon." Shak. While we, inquiring phantoms of a day, Inconstant as the shadows we survey! Boyse.

Synonyms: Mutable; fickle; volatile; unsteady; unstable; changeable; variable; wavering; fluctuating.