Synonyms for Doubt:

n.

reserve, scepticism, a question mark over something, doubt yourself. certain, have second thoughts (about something), have mixed feelings about something, be in doubt, Misdoubt, have an idea, um and ah. amazement (noun)
wonder.
attribute (noun)
doubtfulness, question, dubiousness.
cognition (noun)
uncertainty, incertitude, dubiousness, doubtfulness, dubiety.
disbelief (noun)
agnosticism, misgiving, incertitude, skepticism, cynicism, uncertainty, wariness, disbelief, unbelief, qualm, unsureness.
doubt (noun)
question, doubtfulness, incertitude, dubiousness, dubiety, uncertainty.
doubtless (noun)
beyond the shadow of a doubt, unquestionably, surely, certain, certainly.
equivocation (noun)
ambivalence.
indiscrimination (noun)
confusion, Indiscrimination, indistinguishability.
irresolution (noun)
vacillation.
lack of faith, conviction; questioning (noun)
diffidence, discredit, agnosticism, incertitude, dubiousness, apprehension, scruple, skepticism, quandary, wavering, rejection, reluctance, dilemma, qualm, vacillation, suspense, irresolution, hesitancy, perplexity, suspicion, faithlessness, dubiety, disbelief, misgiving, incredulity, difficulty, ambiguity, distrust, confusion, indecision, uncertainty.
no doubt (noun)
demur, disbelieve, suspect, surely, unquestionably, distrust, waver, certainly, vacillate, question.
qualification (noun)
reservation.
resentment (noun)
jealousy.
uncertainty (noun)
ambivalence, misgiving, incertitude.

v.

doubt (verb)
distrust, vacillate, faithlessness, waver, question, disbelieve, wonder, suspect.
lack confidence in; question (verb)
waver, demur, vacillate, suspect, disbelieve, Misdoubt.

Other synonyms:

suspicious. reserve. anxiety
insecurity.
disagree
demur.
disinclination
reluctance.
indecision
vacillation.
scruple
scruple.
Other relevant words:
perplexity, Misdoubt, reservation, suspicion, indecision, diffidence, hesitancy, jealousy, ambivalence, bewilderment, reluctance, quandary, faithlessness, difficulty, rejection, irresolution, incredulity, discredit, distrustful, timidity, dubiousness, scruple, bashfulness, wavering, ambiguity, apprehension, doubtfulness, dubiety, suspense, dilemma, scepticism, insecurity, reserve, demur, vacillation, certainly, suspicious.

Usage examples for doubt

  1. Now there was no doubt of it! – Jack of the Pony Express by Frank V. Webster
  2. No doubt you- There again! – Charlie to the Rescue by R.M. Ballantyne
  3. That all would go right with Nono she did not doubt – The Golden House by Mrs. Woods Baker