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 doubtfulness

Historical Examples of doubtfulness

  • The doubtfulness as to their adaptability to the representative form of government.

    The Arena


  • She was haunted by an uneasy sense of doubtfulness as to her social position.

  • There was incredulity in the question, but also there was a tinge of doubtfulness too.

    Local Color

    Irvin S. Cobb

  • His replies were oracular neither in brevity nor in doubtfulness of meaning.

  • Mr. Zwiebel looked at his wife with an elaborate assumption of doubtfulness.

British Dictionary definitions for doubtfulness



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 doubtfulness



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

Online Etymology Dictionary, © 2010 Douglas Harper