Impenetrable
Impenetrable adjective - Impossible to get through or into.
Proof is a synonym for impenetrable. In some cases you can use "Proof" instead an adjective "Impenetrable".
Nearby Words: impenetrability, impenetrably
Proof
Proof adjective - (used in combination or as a suffix) able to withstand.
Impenetrable is a synonym for proof in impervious topic. Sometimes you can use "Impenetrable" instead an adjective "Proof", if it concerns topics such as characteristic, resistant.
Mutual synonyms
Both words in one sentence
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Too bad it wasn't bomb proof.Deadpool: How's that for impenetrable, asshole?
Source: Video Game / Deadpool
Cite this Source
Proof and Impenetrable. (2016). Retrieved 2026, August 15, from https://thesaurus.plus/related/impenetrable/proof
Impenetrable & Proof. N.p., 2016. Web. 15 Aug. 2026. <https://thesaurus.plus/related/impenetrable/proof>.
Proof or Impenetrable. 2016. Accessed August 15, 2026. https://thesaurus.plus/related/impenetrable/proof.
Google Ngram Viewer shows how "impenetrable" and "proof" have occurred on timeline