Inconstant, a.
Etymology: [L. inconstans: cf. F. inconstant. See In- not, and Constant.]
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.
Syn. -- Mutable; fickle; volatile; unsteady; unstable; changeable; variable; wavering; fluctuating.
Shades of meaning
Fernald has no entry of its own for inconstant; he lists it under vain.
He lists it without comment; the entries above explain its neighbors.