What does "doubtful" mean?

Doubtful: 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.

Additional senses

  1. 2.Characterized by ambiguity; dubious; as, a doubtful expression; a doubtful phrase.
  2. 3.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.
  3. 4.Fearful; apprehensive; suspicious. [Obs.] I am doubtful that you have been conjunct And bosomed with her. Shak.

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