Dubitative :: Dubitative (a.) Tending to doubt; doubtful.
Indubious :: Indubious (a.) Not dubious or doubtful; certain.
Indubious :: Indubious (a.) Not doubting; unsuspecting.
Indubitable :: Indubitable (a.) Not dubitable or doubtful; too evident to admit of doubt; unquestionable; evident; apparently certain; as, an indubitable conclusion..