Another word for doubtful
in doubt, questionable, problematic, vague, indistinct, unclear, indefinite, undetermined, unresolved, open to doubt, in question, equivocal, unsure, indeterminate, under examination, debatable, theoretical, up in the air*, iffy*, yes and no*, out of focus*; see also obscure 1, questionable 1, uncertain 2.
Uncertain in mind
dubious, doubting, questioning, skeptical, undecided, unsure, wavering, hesitating, ambivalent, undetermined, uncertain, unsettled, confused, disturbed, lost, puzzled, disconcerted, perplexed, discomposed, flustered, flurried, baffled, hesitant, distracted, faltering, unresolved, in a quandary, of two minds, unable to make up one's mind, vacillating, indecisive, irresolute, agnostic, like a doubting Thomas, troubled with doubt, of little faith, faithless, distrustful, incredulous, cynical, not knowing what's what, having no idea, in a dilemma, under a spell*, in the clouds*, up a tree*, in a haze*, not able to make head or tail of*, from Missouri*, going around in circles*, out of one's bearings*, up in the air*, wishy-washy*; see also suspicious 1.
Of questionable character
doubtful implies strong uncertainty as to the probability, value, honesty, validity, etc. of something a doubtful remedy; dubious is less strong, suggesting merely vague suspicion or hesitancy dubious about the future; questionable strictly suggests only that there is some reason for doubt, but it is often used as a euphemism to imply strong suspicion, almost amounting to certainty, of immorality, dishonesty, etc. a questionable reputation; problematic implies only uncertainty with no suggestion of a moral question a problematic success
Another word for doubtfuladjective
Not affording certainty:ambiguous, borderline, chancy, clouded, dubious, dubitable, equivocal, inconclusive, indecisive, indeterminate, problematic, problematical, questionable, uncertain, unclear, unsure. (Informal) iffy. Idioms: at issue, in doubt, in question. See certain, clear
Not likely:improbable, questionable, unapt, unlikely. See likely
Experiencing doubt:dubious, skeptical, uncertain, undecided, unsure. Idiom: in doubt. See certain
In doubt or dispute:arguable, contested, debatable, disputable, exceptionable, moot, mootable, problematic, problematical, questionable, uncertain. See certain
Of dubious character:equivocal, questionable, shady, suspect, suspicious, uncertain. (Informal) fishy. See honest