135 entries under adjective topic. ×

3
fortified(firm, true, fixed, constant)
3
impervious(secure, safe, snug, intact)
3
inextinguishable
3
insurmountable
3
irresistible
3
mighty
3
tough
3
unquenchable
2
absolute
2
conceptive
2
defended(secure, safe, snug, intact)
2
dependable
2
good
2
guarded(secure, safe, snug, intact)
2
immovable(firm, true, fixed, resolute)
2
safeguarded(secure, safe, snug, intact)
2
shielded(secure, safe, snug, intact)
2
unshakable
2
untouchable
1
accented
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APASmart Define. (2015). impregnable thesaurus. Retrieved September 23, 2026, from https://smartdefine.org/impregnable/thesaurus/synonyms
ChicagoSmart Define. 2015. "impregnable thesaurus" https://smartdefine.org/impregnable/thesaurus/synonyms (accessed September 23, 2026).
HarvardSmart Define 2015, impregnable thesaurus, Smart Define, viewed 23 September, 2026, <https://smartdefine.org/impregnable/thesaurus/synonyms>.
MLASmart Define. "impregnable thesaurus" 10 April 2015. Web. 23 September 2026. <https://smartdefine.org/impregnable/thesaurus/synonyms>