Doubt"ful (?), a. 1. 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.
Methinks I should know you, and know this man;
Yet I am doubtful.
Shak.
With doubtful feet and wavering resolution.
Milton.
2. 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.
Beauty is but a vain and doubtful good.
Shak.
Is it a great cruelty to expel from our abode the enemy of our peace, or even the doubtful friend [i. e., one as to whose sincerity there may be doubts]?
Bancroft.
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.
© Webster 1913. | 
