[doubt.ful] adj (14c) 1: giving rise to doubt: open to question "it is ~ that they ever knew what happened"
2. a: lacking a definite opinion, conviction, or determination "they were ~ about the advantages of the new system" b: uncertain in outcome: undecided "the outcome of the election remains ~"
3: marked by qualities that raise doubts about worth, honesty, or validity "of ~ repute" -- doubt.ful.ly adv -- doubt.ful.ness n syn doubtful, dubious, problematic, questionable mean not affording assurance of the worth, soundness, or certainty of something. doubtful implies little more than a lack of conviction or certainty "doubtful about whether I said the right thing". dubious stresses suspicion, mistrust, or hesitation "dubious about the practicality of the scheme". problematic applies esp. to things whose existence, meaning, fulfillment, or realization is highly uncertain "whether the project will ever be finished is problematic". questionable may imply no more than the existence of doubt but usu. suggests that the suspicions are well-grounded "a man of questionable honesty".