impenetrable
Americanadjective
-
not penetrable; that cannot be penetrated, pierced, entered, etc.
-
inaccessible to ideas, influences, etc.
-
incapable of being understood; inscrutable; unfathomable.
an impenetrable mystery.
- Synonyms:
- hidden, obscure, mysterious, incomprehensible
-
Physics. possessing impenetrability.
adjective
-
incapable of being pierced through or penetrated
an impenetrable forest
-
incapable of being understood; incomprehensible
impenetrable jargon
-
incapable of being seen through
impenetrable gloom
-
not susceptible to ideas, influence, etc
impenetrable ignorance
-
physics (of a body) incapable of occupying the same space as another body
Other Word Forms
Etymology
Origin of impenetrable
1425–75; late Middle English impenetrabel < Latin impenetrābilis. See im- 2, penetrable
Explanation
Impenetrable describes something that's impossible to get through. Whether it's a brick wall or a difficult reading passage, something impenetrable won't let you in. Impenetrable comes from the Latin impenetrabilis, meaning "not to put or get into, enter into." Impenetrable, the adjective, has two meanings. When you're trying to learn a subject that is so complicated, so confusing or so detailed that it seems like it's in another language or from another planet, it's impenetrable — like calculus. Or a physical object can be impenetrable, meaning it is impossible to actually enter or get inside of, like that impenetrable nightclub that has bouncers watching every entrance to keep you and your friends out.
Vocabulary lists containing impenetrable
The Diary of Anne Frank
Looking to grow your vocabulary? Check out this interactive, curated word list from our team of English language specialists at Vocabulary.com – one of over 17,000 lists we've built to help learners worldwide!
The Alchemist
Interested in learning more words like this one? Our team at Vocabulary.com has got you covered! You can review flashcards, quiz yourself, practice spelling, and more – and it's all completely free to use!
Tolkien Reading Day, List 1
Want to remember this word for good? Start your learning journey today with our library of interactive, themed word lists built by the experts at Vocabulary.com – we'll help you make the most of your study time!
Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
The journey will require an impenetrable will and a fearlessness to sacrifice everything for the sake of democracy for all.
From Slate ● Jul. 27, 2026
Minutes earlier, the players paraded around Azteca Stadium — traditionally an impenetrable fortress — to applaud El Tri fans with tears in their eyes.
From Los Angeles Times ● Jul. 12, 2026
She’s everything I wasn’t and never would be: aggressively pink, fluffy and wrapped in an impenetrable privilege that appeared to reward her ditziness.
From Salon ● Jul. 6, 2026
But his impenetrable prose -- used to avoid committing to any particular course -- and his confidence in unfettered markets and institutions to correct themselves frustrated critics, who believed the US economy needed stronger guardrails.
From Barron's ● Jun. 22, 2026
In a few steps they were in utter and impenetrable dark.
From "The Two Towers" by J. R. R. Tolkien
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
