22 entries under doubtful topic. ×

12
strange(adjective, excellent, obscure, extraordinary, unusual)
10
rare(adjective, obscure, extraordinary, strange, special)
7
unbelievable(adjective, obscure, extraordinary, strange)
6
inconceivable(adjective, obscure, belief, exceptional, marvelous)
5
unimaginable(adjective, extraordinary, strange, exceptional, special)
4
incredible(adjective, extraordinary, unusual, strange, superb)
3
unlikely(adjective, obscure, extraordinary, strange)
1
absurd(dubious, improbable)
1
implausible(extraordinary, strange, dubious, unbelievable)
1
improbable(extraordinary, strange, dubious, unbelievable)
1
remote(strange, new, dubious, indefinite)
1
unconvincing(extraordinary, strange, dubious, unbelievable)
0
contrary(dubious, improbable)
0
dubious
0
faint(dubious, improbable)
0
not likely(expression, dubious, improbable)
0
not probable(expression, dubious, improbable)
0
out of the ordinary(expression, idiom, exceptional, special)
0
outside chance(expression, dubious, improbable)
0
questionable(dubious, improbable)
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APASmart Define. (2015). unheard-of thesaurus. Retrieved October 1, 2026, from https://smartdefine.org/unheard-of/thesaurus/synonyms
ChicagoSmart Define. 2015. "unheard-of thesaurus" https://smartdefine.org/unheard-of/thesaurus/synonyms (accessed October 1, 2026).
HarvardSmart Define 2015, unheard-of thesaurus, Smart Define, viewed 1 October, 2026, <https://smartdefine.org/unheard-of/thesaurus/synonyms>.
MLASmart Define. "unheard-of thesaurus" 14 April 2015. Web. 1 October 2026. <https://smartdefine.org/unheard-of/thesaurus/synonyms>