Impregnable
Impregnable adjective - Incapable of being defeated, overcome, or subdued.
Serious and impregnable are semantically related. In some cases you can use "Serious" instead an adjective "Impregnable".
Serious
Serious adjective - Not joking or playful in mood or manner.
Impregnable and serious are semantically related. Sometimes you can use "Impregnable" instead an adjective "Serious".
Nearby Words: seriously, seriousness
Both words in one sentence
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Cheese-Eating Surrender Monkeys: Spectacularly averted by the French commandos shown taking Ouistreham, who continue the fight in the face of a nearly impregnable artillery position and some serious casualties.
Source: Film / The Longest Day
Cite this Source
Serious and Impregnable. (2016). Retrieved 2026, July 22, from https://thesaurus.plus/related/impregnable/serious
Impregnable & Serious. N.p., 2016. Web. 22 Jul. 2026. <https://thesaurus.plus/related/impregnable/serious>.
Serious or Impregnable. 2016. Accessed July 22, 2026. https://thesaurus.plus/related/impregnable/serious.
Google Ngram Viewer shows how "impregnable" and "serious" have occurred on timeline