Not settled in opinion; undetermined; wavering; hesitating in belief; also used, metaphorically, of the body when its action is affected by such a state of mind; as, we are doubtful of a fact, or of the propriety of a measure.
Admitting of doubt; not obvious, clear, or certain; questionable; not decided; not easy to be defined, classed, or named; as, a doubtful case, hue, claim, title, species, and the like.
Characterized by ambiguity; dubious; as, a doubtful expression; a doubtful phrase.
I cannot explain it; but when difficulties arise, I am not perplexed or doubtful. I know how to meet them. Anne Sullivan
I think people really marry far too much; it is such a lottery after all, and for a poor woman a very doubtful happiness. Queen Victoria
Life is like music, it must be composed by ear, feeling and instinct, not by rule. Nevertheless one had better know the rules, for they sometimes guide in doubtful cases, though not often. Paracelsus
All those who offer an opinion on any doubtful point should first clear their minds of every sentiment of dislike, friendship, anger or pity. Sallust
I felt more doubtful than usual with 'Goon Squad,' because I knew that the book's genre wasn't easily named - Novel? Stories? Novel-in-stories? - and I worried that its lack of a clear category would count against it. My hopes for it were pretty modest. Jennifer Egan