The Collaborative International Dictionary of English v.0.48:

Doubt \Doubt\ (dout), v. i. [imp. & p. p. Doubted; p. pr. &
   vb. n. Doubting.] [OE. duten, douten, OF. duter, doter,
   douter, F. douter, fr. L. dubitare; akin to dubius doubtful.
   See Dubious.]
   1. To waver in opinion or judgment; to be in uncertainty as
      to belief respecting anything; to hesitate in belief; to
      be undecided as to the truth of the negative or the
      affirmative proposition; to b e undetermined.
      [1913 Webster]

            Even in matters divine, concerning some things, we
            may lawfully doubt, and suspend our judgment.
                                                  --Hooker.
      [1913 Webster]

            To try your love and make you doubt of mine.
                                                  --Dryden.
      [1913 Webster]

   2. To suspect; to fear; to be apprehensive. [Obs.]

   Syn: To waver; vacillate; fluctuate; hesitate; demur;
        scruple; question.
        [1913 Webster]