Meaning of “doubt” - Learner’s Dictionary

doubt

verb [ T ] us uk /daʊt/
I've asked him, but I doubt whether he'll come.I seriously doubt whether they'll be successful.His critics doubt he'll achieve that.I didn't doubt for a moment that he'd support me."Do you think he'll win?" "I doubt it."
FEEL UNCERTAIN

B2 to feel uncertain about something or think that something is not probable:

[ + (that) ] I doubt that I'll get the job.
I doubt if/whether he'll win.
NOT BELIEVE

to not believe someone or something:

Do you have any reason to doubt her?

(Definition of “doubt verb” from the Cambridge Learner’s Dictionary © Cambridge University Press)