18
confident(adjective, weak, timid)
14
certain(adjective, confident, valid, undoubtable)
11
sure(adjective, certain, definite, inevitable)
9
clear(adjective, ambiguous, filled)
9
definite(adjective, obscure)
8
desirous
7
unquestionable(adjective, definite)
6
assured(verb, unsure, indefinite)
6
settled(verb, adjective)
6
conclusive
6
indisputable
6
indubitable(adjective, undoubted)
5
well-documented
4
convinced(verb, adjective)
4
credible
4
absolute
3
definitive
3
incontestable
3
incontrovertible
3
inevitable(adjective, certain, distant)
<1234510>
10 years ago|5.2k views|share |citing 
APASmart Define. (2016). doubtful thesaurus. Retrieved September 24, 2026, from https://smartdefine.org/doubtful/thesaurus/antonyms
ChicagoSmart Define. 2016. "doubtful thesaurus" https://smartdefine.org/doubtful/thesaurus/antonyms (accessed September 24, 2026).
HarvardSmart Define 2016, doubtful thesaurus, Smart Define, viewed 24 September, 2026, <https://smartdefine.org/doubtful/thesaurus/antonyms>.
MLASmart Define. "doubtful thesaurus" 24 March 2016. Web. 24 September 2026. <https://smartdefine.org/doubtful/thesaurus/antonyms>