9 entries under unreasonable topic. ×

16
unlikely(adjective, reasonable, likely)
12
unbelievable
7
implausible(adjective, reasonable, likely)
7
inconceivable(adjective, reasonable, imaginable)
5
improbable(adjective, likely)
5
impossible
4
unimaginable
1
irrational
1
untenable
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APASmart Define. (2015). plausible thesaurus. Retrieved September 28, 2026, from https://smartdefine.org/plausible/thesaurus/antonyms
ChicagoSmart Define. 2015. "plausible thesaurus" https://smartdefine.org/plausible/thesaurus/antonyms (accessed September 28, 2026).
HarvardSmart Define 2015, plausible thesaurus, Smart Define, viewed 28 September, 2026, <https://smartdefine.org/plausible/thesaurus/antonyms>.
MLASmart Define. "plausible thesaurus" 10 April 2015. Web. 28 September 2026. <https://smartdefine.org/plausible/thesaurus/antonyms>