“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:

“When night falls, she cloaks the world in impenetrable darkness.”

— 1991, Varg Vikernes, “Dunkelheit”, performed by Burzum:

“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: