25 entries under doubtful topic. ×

2
improbable(adjective, likely, unlikely, implausible)
2
rare(adjective, light, thin, unusual, exceptional)
1
dubious(unlikely, implausible)
1
far-fetched(unlikely, implausible)
1
flimsy(light, thin, strange, rare)
1
hundred-to-one(unlikely, implausible)
1
iffy(unlikely, implausible)
1
inconceivable(adjective, light, obscure, thin, strange)
1
not expected(expression, unlikely, implausible)
1
not likely(expression, adjective, unlikely, implausible)
1
outside chance(expression, adjective, unlikely, implausible)
1
questionable(unlikely, implausible)
1
slim(unlikely, implausible)
1
slim and none(expression, idiom, unlikely, implausible)
1
unbelievable(unlikely, implausible)
1
uncertain(unlikely, implausible)
1
unconvincing(unlikely, implausible)
1
unimaginable(light, thin, special, rare)
1
unlikely(adjective, light, thin, rare)
1
unsubstantial(unlikely, implausible)
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APASmart Define. (2013). unheard of thesaurus. Retrieved September 29, 2026, from https://smartdefine.org/unheard_of/thesaurus/synonyms
ChicagoSmart Define. 2013. "unheard of thesaurus" https://smartdefine.org/unheard_of/thesaurus/synonyms (accessed September 29, 2026).
HarvardSmart Define 2013, unheard of thesaurus, Smart Define, viewed 29 September, 2026, <https://smartdefine.org/unheard_of/thesaurus/synonyms>.
MLASmart Define. "unheard of thesaurus" 19 May 2013. Web. 29 September 2026. <https://smartdefine.org/unheard_of/thesaurus/synonyms>