doubtful

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 especially 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 usually suggests that the suspicions are well-grounded.

• • a man of questionable honesty