Doubting; hesitating; wavering or fluctuating in opinion, but inclined to doubt.
skeptical; marked by or occasioning doubt or doubt; hard to figure out or relieve of doubt; maybe not distinct or simple; puzzling: since, a dubious concern; a dubious light.
Of unsure occasion or problem: because, a dubious undertaking.
Liable to doubt or suspicion; of doubtful high quality or propriety; debateable: as, a person of questionable character; a dubious exchange; his morals or their methods are questionable. Synonyms Unsettled, undetermined.
skeptical, uncertain, etc. (see obscure, a.); debateable, problematical, puzzling.
How would you define dubious?