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
Recent Examples on the Web
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.
For 82 games and three-plus playoff rounds, the bunker remained impenetrable. — Kristian Winfield, New York Daily News, 9 June 2026 Rake grounds into the upper soil layer to avoid creating an impenetrable mat on the soil surface. — Kim Toscano, Southern Living, 31 May 2026 In the venue’s defense, the arena’s near-impenetrable exterior likely had something to do with its appeal. — Alli Rosenbloom, CNN Money, 1 July 2026 Which is okay, because the XLE serves as something of an impenetrable panic room and command center once parked. — New Atlas, 9 June 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 7 Jul. 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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