impenetrable

adjective

im·​pen·​e·​tra·​ble (ˌ)im-ˈpe-nə-trə-bəl How to pronounce impenetrable (audio)
Synonyms of impenetrable
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
impenetrably
(ˌ)im-ˈpe-nə-trə-blē How to pronounce impenetrable (audio)
adverb

Synonyms of impenetrable

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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
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Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
The pair will share the screen with Will Smith and AnnaSophia Robb, who play two FBI agents investigating a seemingly impossible murder within the impenetrable walls of a maximum-security prison. — Matt Grobar, Deadline, 7 Aug. 2026 There was a metal gate rolled out making the front portion of the plane an impenetrable fortress. — David Hookstead Outkick, FOXNews.com, 7 Aug. 2026 Instead, my trembling body was confronted by an impenetrable wall of rock. — Literary Hub, 6 Aug. 2026 The stormy painting conjures the first moments of In the Hand of Dante, as the titular character, portrayed by Oscar Isaac, scales perilously steep steps to what seems an impenetrable stronghold. — A.d. Amorosi, SPIN, 6 Aug. 2026 See All Example Sentences for impenetrable

Word History

Etymology

Middle English impenetrabel, from Middle French impenetrable, from Latin impenetrabilis, from in- + penetrabilis penetrable

First Known Use

15th century, in the meaning defined at sense 1a

Time Traveler
The first known use of impenetrable was in the 15th century

Rhymes for impenetrable

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Browse Nearby Words

impenetrability
impenetrable
impenetrate
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Cite this Entry

“Impenetrable.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/impenetrable. Accessed 15 Aug. 2026.

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Kids Definition

impenetrable

adjective
im·​pen·​e·​tra·​ble (ˈ)im-ˈpen-ə-trə-bəl How to pronounce impenetrable (audio)
1
: impossible to get through or into
impenetrable walls
impenetrable jungle
2
: impossible to understand
an impenetrable mystery
impenetrability
(ˌ)im-ˌpen-ə-trə-ˈbil-ət-ē
noun
impenetrably
(ˈ)im-ˈpen-ə-trə-blē How to pronounce impenetrable (audio)
adverb

More from Merriam-Webster on impenetrable

Nglish: Translation of impenetrable for Spanish Speakers

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