7
inconceivable(adjective, reasonable, belief, unreasonable, unbelievable)
7
incredible(adjective, unreasonable, unbelievable)
6
unbelievable(adjective, unreasonable, plausible)
5
unthinkable(adjective, unusual, unreasonable, unbelievable, incredible)
4
implausible(adjective, reasonable, unreasonable, likely, unbelievable)
4
improbable(adjective, unreasonable, likely, unbelievable)
4
unimaginable(adjective, unreasonable, unbelievable)
3
dubious(adjective, clear, honest)
3
ridiculous(adjective, stupid, funny)
3
suspicious(adjective, careless, certain, doubtful, fishy)
3
unconvincing(adjective, unreasonable, unbelievable, persuasive)
3
unlikely(adjective, reasonable, unreasonable, likely, unbelievable)
3
unreliable(adjective, unreasonable, unbelievable)
2
far-fetched(adjective, hard, natural)
2
doubtful
2
fantastic
2
impossible
2
preposterous
2
questionable
2
tall(adjective, unreasonable, little, exaggerated)
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APASmart Define. (2015). believable thesaurus. Retrieved September 23, 2026, from https://smartdefine.org/believable/thesaurus/antonyms
ChicagoSmart Define. 2015. "believable thesaurus" https://smartdefine.org/believable/thesaurus/antonyms (accessed September 23, 2026).
HarvardSmart Define 2015, believable thesaurus, Smart Define, viewed 23 September, 2026, <https://smartdefine.org/believable/thesaurus/antonyms>.
MLASmart Define. "believable thesaurus" 14 April 2015. Web. 23 September 2026. <https://smartdefine.org/believable/thesaurus/antonyms>