Deep
Deep adjective - Being beyond one's powers to know, understand, or explain.
Usage example: a deep, dark secret that he took to his grave
Impenetrable is a synonym for deep in profound topic. In some cases you can use "Impenetrable" instead an adjective "Deep", when it comes to topics like secret.
Impenetrable
Impenetrable adjective - Being beyond one's powers to know, understand, or explain.
Usage example: the mysteries of that religion are completely impenetrable to outsiders
Deep is a synonym for impenetrable. Sometimes you can use "Deep" instead an adjective "Impenetrable".
Nearby Words: impenetrability, impenetrably
Mutual synonyms
Related pairs
Both words in one sentence
- His friends know where he's being kept, but the dungeon lies deep within the villain's impenetrable fortress, surrounded by guards, and a good old-fashioned prison break simply won't do.
Source: Prisoner Exchange - The Kantri have two thousand years of natural life and grow throughout those, every fifty years or so going into a Deep Sleep and shedding their lobsterlike nigh-impenetrable armor.
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By finding an item hidden deep in a maze of the same color and bringing it into the right room, one could move though a previously impenetrable barrier, where the text "Created by Warren Robinett" could be found.
Source: Easter Egg
Cite this Source
Impenetrable and Deep. (2016). Retrieved 2026, August 15, from https://thesaurus.plus/related/deep/impenetrable
Deep & Impenetrable. N.p., 2016. Web. 15 Aug. 2026. <https://thesaurus.plus/related/deep/impenetrable>.
Impenetrable or Deep. 2016. Accessed August 15, 2026. https://thesaurus.plus/related/deep/impenetrable.
Google Ngram Viewer shows how "deep" and "impenetrable" have occurred on timeline