1. (v. i.) 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.

2. (v. i.) To suspect; to fear; to be apprehensive.

3. (v. t.) To question or hold questionable; to withhold assent to; to hesitate to believe, or to be inclined not to believe; to withhold confidence from; to distrust; as, I have heard the story, but I doubt the truth of it.

4. (v. t.) To suspect; to fear; to be apprehensive of.

5. (v. t.) To fill with fear; to affright.

6. (n.) A fluctuation of mind arising from defect of knowledge or evidence; uncertainty of judgment or mind; unsettled state of opinion concerning the reality of an event, or the truth of an assertion, etc.; hesitation.

7. (v. i.) Uncertainty of condition.

8. (v. i.) Suspicion; fear; apprehension; dread.

9. (v. i.) Difficulty expressed or urged for solution; point unsettled; objection.

Humism Pyrrhonism agnosticism agonize over all-overs anxiety apprehension apprehensiveness awake a doubt be at sea be diffident be doubtful be dubious be possessive be skeptical be uncertain beat about call in question challenge concern confutability contest contestability controvertibility deniability diffidence disbelief disbelieve discredit disputability dispute disquiet distrust distrustfulness doubtful doubtfulness dubiety dubiousness dubitancy fear feel unsure flounder fluctuate foreboding greet with skepticism grope half believe half-belief harbor suspicions have reservations hesitate hesitation in doubt incertitude incredulity irresolution leeriness misdoubt misgive misgiving mistrust mistrustfulness puzzle over qualm qualmishness query question questionableness raise a question refutability reservations scepticism scoff scoffing scruple scrupulousness self-doubt shadow of doubt skepticalness skepticism smell a rat suspect suspicion suspiciousness thrash about throw doubt upon total skepticism treat with reserve unbelief uncertainty vacillate wariness waver wonder wonder whether worry