Synonyms and related words :
agnostic, ambiguous, capricious, chancy, changeable, controvertible, dicey, doubting, equivocal, erratic, fickle, hesitant, hesitating, incalculable, indecisive, indemonstrable, irresolute, polysemous, skeptical, touch-and-go, unaccountable, unattestable, uncertain, unconfirmable, unconvinced, undemonstrable, undemonstratable, undivinable, unforeseeable, unpersuaded, unpredictable, unsubstantiatable, unsupportable, unsure, unsustainable, unverifiable, variable, wavering, whimsical