Etymology From Middle English inpenetrabel, inpenetrabyle, from Middle French impenetrable or directly from its etymon, Latin impenetrābilis. By surface analysis, im- + penetrable.
1
Not penetrable.
The fortress is impenetrable, so it cannot be taken.
The avalanche spread and stopped, locking everything it carried into an icy cocoon. It was now a jagged, virtually impenetrable pile of ice, longer than a football field and nearly as wide.2012, John Branch, “Snow fall: The avalanche at Tunnel Creek”, in The New York Times, New York, N.Y.: The New York Times Company, →ISSN, →OCLC, archived from the original on 11 Jun 2024:
2
Opaque; obscure; not translucent or transparent.
When night falls, she cloaks the world in impenetrable darkness.1991, Varg Vikernes, “Dunkelheit”, performed by Burzum:
Etymology From Middle English inpenetrabel, inpenetrabyle, from Middle French impenetrable or directly from its etymon, Latin impenetrābilis. By surface analysis, im- + penetrable.
1
A person not openly given to friendship.
I should lose the reputation that I am gradually acquiring among our impenetrables here, were I to confess the excitement which I felt at the idea of entering his house—the house of that great general under whose command you made your first charge.1837, L[etitia] E[lizabeth] L[andon], “Chapter XXVI. Lady Marchmont to Sir Jasper Meredith.”, in Ethel Churchill: Or, The Two Brides. […], volume I, London: Henry Colburn, […], →OCLC, page 236: