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

In January 1915, their ship, the Endurance, became trapped in the thick, impenetrable ice of the Weddell Sea. —Tony Bradley, Forbes, 15 Oct. 2024

Contractors claimed their prototypes would turn America into an impenetrable fortress. —Outside Online, 9 Oct. 2024

Norman Reedus promises the 'best hour of Walking Dead ever' on season 2 of Daryl Dixon No character in The Walking Dead universe is harder to get closer to than Daryl, who locks his heart in a fortress more impenetrable than the Sanctuary. —EW.com, 19 Sep. 2024

Indeed, there’s something altogether impenetrable about Pavement’s shaggy, brilliant lead man, which may explain some of the fascination the band has held over the years. —Jordan Mintzer, The Hollywood Reporter, 4 Sep. 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