Synonyms|713Antonyms|152|Broader|9Narrower|8Related|663
4
ungraspable(adjective, incomprehensible)
4
weighty
3
airtight(adjective, fast, short, uncomfortable, resistant)
3
closed
3
crowded(adjective, close, set, solid, heavy)
3
dull(adjective, dark, gloomy, dense, cloudy)
3
enigmatical(adjective, solid, strange, supernatural, dense)
3
fleshy
3
indomitable
3
inexpugnable
3
inflexible(adjective, set, strong, hard, tough)
3
resistant(adjective, hard, unfeeling, unsympathetic, prepared)
3
rigid(adjective, set, strong, hard, tough)
3
strong(adjective, close, set, hard, secure)
3
unconquerable
3
undecipherable(adjective, unintelligibility)
3
undiscoverable(adjective, hidden, unfathomable, incomprehensible, enigmatic)
3
unpassable
2
accented
2
anesthetic
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APASmart Define. (2015). impenetrable thesaurus. Retrieved September 24, 2026, from https://smartdefine.org/impenetrable/thesaurus/synonyms
ChicagoSmart Define. 2015. "impenetrable thesaurus" https://smartdefine.org/impenetrable/thesaurus/synonyms (accessed September 24, 2026).
HarvardSmart Define 2015, impenetrable thesaurus, Smart Define, viewed 24 September, 2026, <https://smartdefine.org/impenetrable/thesaurus/synonyms>.
MLASmart Define. "impenetrable thesaurus" 10 April 2015. Web. 24 September 2026. <https://smartdefine.org/impenetrable/thesaurus/synonyms>