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

With speculators and short sellers focused on technical indicators, the seemingly impenetrable $50 level was an easy read. —John S. Tobey, Forbes, 2 Nov. 2024

Will this tour win over new fans to Soul Coughing’s sometimes impenetrable music? —Jeff Miller, Variety, 12 Sep. 2024

Just as Lewis’s beloved book found humanity in seemingly impenetrable data, so too does Chris Mark’s lifelong quest become as riveting as a rescue mission. —Peter Rubin, Longreads, 6 Sep. 2024

In January 1915, their ship, the Endurance, became trapped in the thick, impenetrable ice of the Weddell Sea. —Tony Bradley, Forbes, 15 Oct. 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