60 entries under implausible topic. ×

30
unimaginable(adjective, belief, unreasonable, useless, size)
22
impossible(adjective, extraordinary, belief, unreasonable, dubious)
22
incredible(adjective, great, flat, poor, thin)
22
unbelievable(adjective, great, obscure, flat, poor)
13
improbable(adjective, great, flat, poor, thin)
11
preposterous(adjective, obscure, unreasonable, useless, absurd)
10
unlikely(adjective, light, obscure, thin, belief)
8
rare(adjective, obscure, extraordinary, unusual, belief)
7
doubtful(adjective, extraordinary, unreasonable, amazing, dubious)
7
thin(adjective, light, weak, great, poor)
7
unconvincing(adjective, great, flat, poor, thin)
6
beyond belief(expression, adjective, idiom, belief, absurd)
6
flimsy(adjective, light, unreasonable, rare, likely)
6
ridiculous(adjective, absurd, unbelievable, preposterous)
6
weak(adjective, great, poor, informal, extraordinary)
5
dubious(adjective, extraordinary, unreasonable, amazing, doubtful)
5
outlandish(obscure, extraordinary, absurd, unknown)
5
questionable(adjective, extraordinary, amazing, doubtful, dubious)
5
unsubstantial(adjective, thin, extraordinary, belief, unreasonable)
4
suspect(extraordinary, unreasonable, dubious, absurd, flimsy)
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APASmart Define. (2015). inconceivable thesaurus. Retrieved September 21, 2026, from https://smartdefine.org/inconceivable/thesaurus/synonyms
ChicagoSmart Define. 2015. "inconceivable thesaurus" https://smartdefine.org/inconceivable/thesaurus/synonyms (accessed September 21, 2026).
HarvardSmart Define 2015, inconceivable thesaurus, Smart Define, viewed 21 September, 2026, <https://smartdefine.org/inconceivable/thesaurus/synonyms>.
MLASmart Define. "inconceivable thesaurus" 14 April 2015. Web. 21 September 2026. <https://smartdefine.org/inconceivable/thesaurus/synonyms>