Impregnable
Impregnable adjective - Incapable of being defeated, overcome, or subdued.
Usage example: an impregnable fortress that had foiled one invader after another over the centuries
Secure is a synonym for impregnable in invulnerable topic. In some cases you can use "Secure" instead an adjective "Impregnable", when it comes to topics like property, unyielding.
Secure
Secure adjective - Providing safety.
Usage example: escaped to a secure location
Impregnable is a synonym for secure in safe topic. You can use "Impregnable" instead an adjective "Secure", if it concerns topics such as protected from danger.
Mutual synonyms
Cite this Source
Secure and Impregnable. (2016). Retrieved 2026, July 21, from https://thesaurus.plus/related/impregnable/secure
Impregnable & Secure. N.p., 2016. Web. 21 Jul. 2026. <https://thesaurus.plus/related/impregnable/secure>.
Secure or Impregnable. 2016. Accessed July 21, 2026. https://thesaurus.plus/related/impregnable/secure.
Google Ngram Viewer shows how "impregnable" and "secure" have occurred on timeline