doubtful

[dout-fuh l] /ˈdaʊt fəl/
adjective
1.
of uncertain outcome or result.
2.
admitting of or causing doubt; uncertain; ambiguous.
3.
unsettled in opinion or belief; undecided; hesitating.
4.
of equivocal or questionable character:
His tactics are highly doubtful.
Origin
1350-1400; Middle English douteful. See doubt, -ful
Related forms
doubtfully, adverb
doubtfulness, noun
predoubtful, adjective
predoubtfully, adverb
quasi-doubtful, adjective
quasi-doubtfully, adverb
undoubtful, adjective
undoubtfully, adverb
undoubtfulness, noun
Synonyms
1. undetermined, unsettled, indecisive, dubious, problematic. 2. unsure, indeterminate. 3. irresolute, vacillating, hesitant. 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. 4. shady.
Antonyms
1, 2. certain.
Usage note
See doubt.
Examples from the web for doubtful
  • Whether the settlement will raise much money is doubtful.
  • But even there it is doubtful that your green plans are that unusual.
  • It is doubtful he would have achieved acclaim without it.
  • It is doubtful that the princes appreciated the courtesy.
  • It's doubtful that they experience any pain, they may actually derive joy from being at odds with the particular group.
  • Immediately, there was scepticism from experts doubtful about any surviving human dodos.
  • It is doubtful that anyone would take their own life because their career didn't turn out exactly as they planned.
  • Some people remain doubtful that what is happening here can succeed, or be controlled.
  • It is doubtful if any one invention has revolutionised any one activity more than gunpowder revolutionised war.
  • Whether he would be better remembered today had he not so decisively retired is doubtful.
British Dictionary definitions for doubtful

doubtful

/ˈdaʊtfʊl/
adjective
1.
unlikely; improbable
2.
characterized by or causing doubt; uncertain: a doubtful answer
3.
unsettled; unresolved
4.
of questionable reputation or morality
5.
having reservations or misgivings
6.
(of a sportsperson) not likely to be fit enough to play or take part
noun
7.
a person who is undecided or uncertain about an issue
8.
a sportsperson who is not likely to be fit enough to play or take part
Derived Forms
doubtfully, adverb
doubtfulness, noun
Usage note
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
Word Origin and History for doubtful
adj.

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