impregnable

1 of 2

adjective

im·​preg·​na·​ble im-ˈpreg-nə-bəl 

1

: incapable of being taken by assault : unconquerable

an impregnable fortress

2

: unassailable

also : impenetrable

impregnable walls

impregnability

(ˌ)im-ˌpreg-nə-ˈbi-lə-tē 

noun

impregnableness

im-ˈpreg-nə-bəl-nəs 

noun

impregnably

im-ˈpreg-nə-blē 

adverb

impregnability

2 of 2

noun

im·​preg·​na·​bil·​i·​ty (¦)imˌpregnəˈbilətē 

əm-, 

-lətē, 

-i

plural -es

: the quality or state of being impregnable

Did you know?

Impregnable is one of the many English words that bear a French ancestry, thanks to the Norman conquest of England in 1066. It derives from the Middle French verb prendre, which means "to take or capture." Combining prendre with various prefixes has given our language many other words, too, including surprise, reprise, and enterprise. Remarkably, impregnable has a different origin from the similar-looking word pregnant; that word comes from a different Latin word, praegnas, meaning "carrying a fetus."

Synonyms of impregnable

Adjective

• invincible
• invulnerable
• unconquerable
• insurmountable
• bulletproof
• unstoppable
• unbeatable
• indomitable
• armored
• insuperable
• undefeated

Examples of impregnable in a Sentence

Adjective

an impregnable fortress that had foiled one invader after another over the centuries

the castle's supposedly impregnable walls

Recent Examples on the Web

Adjective

After the Spanish Navy built its arsenal and shipyards in Ferrol’s almost impregnable harbor in the 18th century, the city boomed. — Jason Horowitz, New York Times, 28 Oct. 2026

The bottom line is that the control of the Amodeis and their co-founders is designed to be impregnable. — Business Columnist, Los Angeles Times, 28 Oct. 2026

Their security infrastructure is more impregnable than that of a bank. — Gideon Lewis-Kraus, New Yorker, 19 Oct. 2026

Dropped catches from Steve Smith, Green and Travis Head ensured yesterday's brief rally in the field fizzled out and allowed Bangladesh to bat itself into an almost impregnable position. — ABC News, 14 Aug. 2026

Word History

Etymology

Adjective

Middle English imprenable, from Middle French, from in- + prenable vulnerable to capture, from prendre to take — more at prize

First Known Use

Adjective

15th century, in the meaning defined at sense 1

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Kids Definition

impregnable

adjective

im·​preg·​na·​ble im-ˈpreg-nə-bəl 

: not able to be captured by assault : unconquerable

an impregnable fortress

impregnably

-blē 

adverb