impenetrable
adjective
im·pen·e·tra·ble
(ˌ)im-ˈpe-nə-trə-bəl 
1
a
: incapable of being penetrated or pierced
impenetrable armor
b
: inaccessible to knowledge, reason, or sympathy : impervious
an impenetrable heart
2
: incapable of being comprehended : inscrutable
an impenetrable mystery
Synonyms of impenetrable
Examples of impenetrable in a Sentence
The fort's defenses were thought to be impenetrable.
the ancient temple was surrounded by vast stretches of impenetrable jungle
Recent Examples on the Web
Blogs, tweets, and podcasts bypass traditional gatekeepers, bringing a wider array of voices into literary spaces that once seemed impenetrable.
—
Literary Hub, 18 Feb. 2026
For decades, Silicon Valley has maintained a nearly impenetrable legal perimeter in the form of Section 230 of the Communications Decency Act, a 1996 law that allows tech companies to avoid legal responsibility for what its users post.
—Bobby Allyn, NPR, 18 Feb. 2026
The series retains its fondness for rapid-fire, near-impenetrable finance jargon and for ostentatious literary quotations—the product, we’re meant to assume, of the characters’ otherwise wasted Oxbridge educations.
—Inkoo Kang, New Yorker, 9 Feb. 2026
This behavior is designed to make the people feel powerless and the governing authority impenetrable.
—Elizabeth Shackelford, Chicago Tribune, 6 Feb. 2026
See All Example Sentences for impenetrable
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Literary Hub, 18 Feb. 2026
For decades, Silicon Valley has maintained a nearly impenetrable legal perimeter in the form of Section 230 of the Communications Decency Act, a 1996 law that allows tech companies to avoid legal responsibility for what its users post.
—Bobby Allyn, NPR, 18 Feb. 2026
The series retains its fondness for rapid-fire, near-impenetrable finance jargon and for ostentatious literary quotations—the product, we’re meant to assume, of the characters’ otherwise wasted Oxbridge educations.
—Inkoo Kang, New Yorker, 9 Feb. 2026
This behavior is designed to make the people feel powerless and the governing authority impenetrable.
—Elizabeth Shackelford, Chicago Tribune, 6 Feb. 2026
See All Example Sentences for impenetrable
Cite this Entry
“Impenetrable.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/impenetrable. Accessed 24 Feb. 2026.
Copy CitationKids Definition
impenetrable
adjective
im·pen·e·tra·ble
(ˈ)im-ˈpen-ə-trə-bəl
1
: impossible to get through or into
impenetrable walls
impenetrable jungle
2
: impossible to understand
an impenetrable mystery
impenetrability
noun
(ˌ)im-ˌpen-ə-trə-ˈbil-ət-ē
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