of uncertain outcome or result.
admitting of or causing doubt; uncertain; ambiguous.
unsettled in opinion or belief; undecided; hesitating.
of equivocal or questionable character: His tactics are highly doubtful.

Origin of doubtful

First recorded in 1350–1400, doubtful is from the Middle English word douteful. See doubt, -ful
Related formsdoubt·ful·ly, adverbdoubt·ful·ness, nounpre·doubt·ful, adjectivepre·doubt·ful·ly, adverbqua·si-doubt·ful, adjectivequa·si-doubt·ful·ly, adverbun·doubt·ful, adjectiveun·doubt·ful·ly, adverbun·doubt·ful·ness, noun

Synonyms for doubtful

Synonym study

3. Doubtful, dubious, incredulous, skeptical imply reluctance or unwillingness to be convinced. To be doubtful about something is to feel that it is open to question or that more evidence is needed to prove it: to be doubtful about the statements of witnesses. Dubious implies vacillation, unsureness, or suspicion: dubious about suggested methods of manufacture. Incredulous means unwilling or reluctant to believe: incredulous at the good news. Skeptical implies a general disposition to doubt or question: skeptical of human progress.

Antonyms for doubtful

1, 2. certain.

Usage note

See doubt. Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for doubtful

Contemporary Examples of doubtful

Historical Examples of doubtful

  • In the broad pathways of the ocean such a chance is doubtful.

    Brave and Bold

    Horatio Alger

  • And, if we do, it is doubtful if we can attract their attention.

    Brave and Bold

    Horatio Alger

  • My errors, however, have at least made me cautious and doubtful of my own conclusions.

    'Tis Sixty Years Since

    Charles Francis Adams

  • It is doubtful if it was mentally prepared to entertain it, or evolve the idea.

  • It is doubtful if many of the others were any better off in this respect.

British Dictionary definitions for doubtful



unlikely; improbable
characterized by or causing doubt; uncertaina doubtful answer
unsettled; unresolved
of questionable reputation or morality
having reservations or misgivings
(of a sportsperson) not likely to be fit enough to play or take part


a person who is undecided or uncertain about an issue
a sportsperson who is not likely to be fit enough to play or take part
Derived Formsdoubtfully, adverbdoubtfulness, noun


It was formerly considered correct to use whether after doubtful (it is doubtful whether he will come), but now if and that are also acceptable
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for doubtful

late 14c., from doubt (n.) + -ful. Related: Doubtfully; doubtfulness.

Online Etymology Dictionary, © 2010 Douglas Harper