8 entries under impossible topic. ×

12
insurmountable(adjective, do, unreasonable, useless, remote)
2
unattainable(adjective, inaccessible, impossibility)
1
unapproachable(unaffected, unyielding, unbending, resistant, unreceptive)
0
challenging(adjective, insuperable, insurmountable)
0
overwhelming(adjective, hopeless, insuperable, insurmountable)
0
undefeatable(adjective, strong, secure, resolute, steadfast)
0
unrealizable
0
unworkable
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APASmart Define. (2015). impassable thesaurus. Retrieved September 20, 2026, from https://smartdefine.org/impassable/thesaurus/synonyms
ChicagoSmart Define. 2015. "impassable thesaurus" https://smartdefine.org/impassable/thesaurus/synonyms (accessed September 20, 2026).
HarvardSmart Define 2015, impassable thesaurus, Smart Define, viewed 20 September, 2026, <https://smartdefine.org/impassable/thesaurus/synonyms>.
MLASmart Define. "impassable thesaurus" 14 April 2015. Web. 20 September 2026. <https://smartdefine.org/impassable/thesaurus/synonyms>