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

Lynch wove tales, not unlike those of his Spanish predecessor Luis Bunuel, which proceeded with their own impenetrable logic. —Chris Morris, Variety, 16 Jan. 2025

This time, Nick tracks Donnie down not to arrest him but to join his criminal enterprise, the Panthers, and stage a heist of the impenetrable World Diamond Center. —Robert Daniels, New York Times, 10 Jan. 2025

China has become increasingly aggressive in the region as climate change reduces much of the impenetrable Arctic Circle ice to water, Bolton said. —Josh Meyer, USA TODAY, 9 Jan. 2025

Studying Trump’s image-making is, for better or worse, one of the few windows into the worldview of an otherwise impenetrable figure. —Leah Dolan, CNN, 18 Jan. 2025

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