4
unreceptive(adjective, unyielding, unbending, unable, disinclined)
4
unsympathetic(adjective, bad, cold, indifferent, detached)
3
apathetic(adjective, indifferent, detached, distant, unfeeling)
3
closed
3
closed to(expression, adjective, unyielding, unbending, unable)
3
cold(adjective, calm, indifferent, restrained, detached)
3
deaf
3
emotionless(adjective, bad, cold, aloof, no feelings)
3
frigid
3
hard-boiled(noun, adjective, calm, bad, cold)
3
hard-hearted(adjective, calm, bad, cold, restrained)
3
impregnable(adjective, secure, safe, snug, intact)
3
inflexible(adjective, hard, tough, solid, rigid)
3
leakproof(adjective, watertight)
3
soundproof
3
steely
3
thick(adjective, hard, solid, rigid, dense)
3
tough(noun, adjective, set, strong, hard)
3
unconcerned(adjective, calm, indifferent, restrained, detached)
3
unpassable
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APASmart Define. (2015). impervious thesaurus. Retrieved September 22, 2026, from https://smartdefine.org/impervious/thesaurus/synonyms
ChicagoSmart Define. 2015. "impervious thesaurus" https://smartdefine.org/impervious/thesaurus/synonyms (accessed September 22, 2026).
HarvardSmart Define 2015, impervious thesaurus, Smart Define, viewed 22 September, 2026, <https://smartdefine.org/impervious/thesaurus/synonyms>.
MLASmart Define. "impervious thesaurus" 14 April 2015. Web. 22 September 2026. <https://smartdefine.org/impervious/thesaurus/synonyms>