adjective
doubtful
Synonyms: arguable, chancy, debatable, diffident, disputable, dubitable, equivocal, far-fetched, fishy, fly-by-night, hesitant, iffy, improbable, indecisive, moot, mootable, open, perplexed, problematic, questionable, reluctant, shady, skeptical, suspect, suspicious, touch and go, trustless, unassured, uncertain, unclear, unconvinced, undecided, undependable, unlikely, unreliable, unsure, untrustworthy, untrusty, wavering
Antonyms: certain, definite, doubtless, positive, reliable, sure, trustworthy, trusty, undoubtful
adjective
vague, unclear
Synonyms: ambiguous, debatable, disinclined, doubtful, equivocal, indefinite, indeterminate, mistrustful, obscure, open, problematic, problematical, undecided, unsettled
Antonyms: certain, clear, definite, unambiguous, unobscure