3. Characterized by ambiguity; dubious; as, a doubtful expression; a doubtful phrase.

4. Of uncertain issue or event. We . . . have sustained one day in doubtful fight. Milton. The strife between the two principles had been long, fierce, and doubtful. Macaulay.

5. Fearful; apprehensive; suspicious. [Obs.] I am doubtful that you have been conjunct And bosomed with her. Shak.

Syn. — Wavering; vacillating; hesitating; undetermined; distrustful; dubious; uncertain; equivocal; ambiguous; problematical; questionable.

DOUBTFULLY
Doubt"ful*ly, adv.

Defn: In a doubtful manner.
Nor did the goddess doubtfully declare. Dryden.

DOUBTFULNESS
Doubt"ful*ness, n.

1. State of being doubtful.

2. Uncertainty of meaning; ambiguity; indefiniteness. " The doubtfulness of his expressions." Locke.

3. Uncertainty of event or issue. Bacon.