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.(noun)
source: webster1913
verb (v)
consider unlikely or have doubts about(verb.cognition)
Example: I doubt that she will accept his proposal of marriage.
source: wordnet30
lack confidence in or have doubts about(verb.cognition)
Example: I doubt these reports.
source: wordnet30
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.(verb)
source: webster1913
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.(verb)