5
unlikely(adjective, adverb, reasonable, unmistakably, possibly)
5
doubtful
4
eye-opening
4
implausible(adjective, reasonable, likely, unlikely, plausible)
4
impossible(adjective, unlikely)
4
improbable(adjective, likely)
4
inconceivable(adjective, reasonable, imaginable)
3
foul
3
incredible
3
outside(adjective, slight, slim, middle)
3
unbelievable(adjective, plausible)
2
dubious(adjective, clear, honest)
2
fantastic
2
farfetched(adjective, unbelieveable)
2
fishy(adjective, doubtful, suspicious)
2
flimsy
2
remote(adjective, unlikely, improbable)
2
underdog
2
unimaginable
2
unthinkable
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APASmart Define. (2016). likely thesaurus. Retrieved September 22, 2026, from https://smartdefine.org/likely/thesaurus/antonyms
ChicagoSmart Define. 2016. "likely thesaurus" https://smartdefine.org/likely/thesaurus/antonyms (accessed September 22, 2026).
HarvardSmart Define 2016, likely thesaurus, Smart Define, viewed 22 September, 2026, <https://smartdefine.org/likely/thesaurus/antonyms>.
MLASmart Define. "likely thesaurus" 29 March 2016. Web. 22 September 2026. <https://smartdefine.org/likely/thesaurus/antonyms>