impenetrable

adjective

im·​pen·​e·​tra·​ble (ˌ)im-ˈpe-nə-trə-bəl 

1

a

: incapable of being penetrated or pierced

b

: inaccessible to knowledge, reason, or sympathy : impervious

2

: incapable of being comprehended : inscrutable

impenetrably

(ˌ)im-ˈpe-nə-trə-blē 

adverb

Synonyms

• impassable
• impassible
• impermeable
• impervious
• impregnable

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

Some executives believe that AI development will itself sooner or later migrate to impenetrable bunkers whose supercomputers will be powered with nuclear reactors. —Henry A. Kissinger, Foreign Affairs, 18 Nov. 2024

Ahead, an impenetrable tangle of pine forest that's home to all manner of bird and beast. —Arati Menon, Condé Nast Traveler, 10 Nov. 2024

As Raya — now pursuing a new and dangerous story of massive government tax fraud — begins to lose the impenetrable steeliness that’s always enabled her to do her job, her visions of Chovka start to twist and morph, their shadows lengthening. —Sara Holdren, Vulture, 15 Oct. 2024

With every update that makes these devices moderately better, the impenetrable wall of Windows becomes more obvious. —Eric Ravenscraft, WIRED, 31 Aug. 2024

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

Kids 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

(ˌ)im-ˌpen-ə-trə-ˈbil-ət-ē

noun

impenetrably

(ˈ)im-ˈpen-ə-trə-blē 

adverb