dubious
1 doubtful, hesitant, iffy (informal) leery (slang) sceptical, uncertain, unconvinced, undecided, unsure, wavering
2 ambiguous, debatable, dodgy (Brit., Austral., & N.Z. informal) doubtful, equivocal, indefinite, indeterminate, obscure, problematical, unclear, unsettled
3 dodgy (Brit., Austral., & N.Z. informal) fishy (informal) questionable, shady (informal) suspect, suspicious, undependable, unreliable, untrustworthy
Antonyms
certain, definite, dependable, obvious, positive, reliable, sure, trustworthy