FICKLE

adj. flighty, capricious, frivolous, unpredictable, moody, giddy, fanciful, whimsical, fitful, mercurial, volatile, unstable, changeable, mutable, inconstant, changeful, unsteady, unsteadfast, indecisive, undecided, vacillating or rarely vacillant, unsure, uncertain, irresolute, wavering, erratic, unreliable, undependable, irresponsible, untrustworthy, faithless, unfaithful, disloyal, Colloq wishy-washy That fickle woman has already taken up with someone else You should know how fickle the tastes of the public are.