Impregnable
Impregnable adjective - Impossible to get through or into.
Usage example: the castle's supposedly impregnable walls
Solid and impregnable are semantically related. in property topic. In some cases you can use "Solid" instead an adjective "Impregnable", when it comes to topics like unyielding.
Solid
Solid adjective - Based on sound reasoning or information.
Impregnable and solid are semantically related. Sometimes you can use "Impregnable" instead an adjective "Solid".
Mutual synonyms
Both words in one sentence
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The defensive ones make their defending units rock-solid and their cities almost impregnable.
Cite this Source
Solid and Impregnable. (2016). Retrieved 2026, August 10, from https://thesaurus.plus/related/impregnable/solid
Impregnable & Solid. N.p., 2016. Web. 10 Aug. 2026. <https://thesaurus.plus/related/impregnable/solid>.
Solid or Impregnable. 2016. Accessed August 10, 2026. https://thesaurus.plus/related/impregnable/solid.
Google Ngram Viewer shows how "impregnable" and "solid" have occurred on timeline