impermeable

adjective

im·​per·​me·​able (ˌ)im-ˈpər-mē-ə-bəl 

: not permitting passage (as of a fluid) through its substance

broadly : impervious

impermeability

(ˌ)im-ˌpər-mē-ə-ˈbi-lə-tē 

noun

Synonyms

• impassable
• impassible
• impenetrable
• impervious
• impregnable

Examples of impermeable in a Sentence

an impermeable layer of rock

a fabric impermeable to moisture

Recent Examples on the Web

Achieving that often meant forgoing impermeable materials and permanent designs, which stands in stark contrast to the way modern-day water management works are constructed. —Ari Caramanica, The Conversation, 8 Apr. 2025

Taxing cruise ships with foreign flags seems like a simple concept, like building an impermeable border wall. —Roger Dooley, Forbes, 22 Feb. 2025

The impermeable bottom layer is deep in some areas – close to 600 feet – and shallow in others – like 50 feet. —Daniel Desrochers, Kansas City Star, 16 Jan. 2025

As Hurricane Milton is expected to bring record-breaking storm surge yet again to the region, the hospital -- located on the bay near downtown Tampa -- is surrounded by the water-impermeable barrier once more. —Meredith Deliso, ABC News, 9 Oct. 2024

Word History

Etymology

Late Latin impermeabilis, from Latin in- + Late Latin permeabilis permeable

First Known Use

1661, in the meaning defined above

Rhymes for impermeable

• permeable
• semipermeable

Kids Definition

impermeable

adjective

im·​per·​me·​able (ˈ)im-ˈpər-mē-ə-bəl 

: not permitting passage (as of a fluid) through the material of which it is made

impermeability

(ˌ)im-ˌpər-mē-ə-ˈbil-ət-ē 

noun

Medical Definition

impermeable

adjective

im·​per·​me·​able (ˈ)im-ˈpər-mē-ə-bəl 

: not permitting passage (as of a fluid) through its substance

the plasma membrane of a red blood cell is relatively impermeable to sodium and calcium ions

impermeability

(ˌ)im-ˌpər-mē-ə-ˈbil-ət-ē 

noun

plural impermeabilities