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 of impermeable

• impervious
• dense
• close
• impenetrable
• impassable
• impregnable
• thick

Examples of impermeable in a Sentence

an impermeable layer of rock

a fabric impermeable to moisture

Recent Examples on the Web

But as the AfD gains clout through regional elections, the debate within the CDU over exactly how impermeable that firewall should be is also intensifying. — Anna Noryskiewicz, CBS News, 18 Sep. 2026

As communities grow, natural landscapes are frequently replaced by roads, parking lots, rooftops and other impermeable surfaces. — Patty Templeton-Jones, Forbes.com, 18 Sep. 2026

Rain watered crops, and soaked in to recharge the groundwater that hydrated the city — something that can’t happen now, when something like 40% of the city is covered over, impermeable to rain. — Patt Morrison, Los Angeles Times, 17 Sep. 2026

Playing the American League’s best team, the Padres had the final two games of the series in hand before the practically impermeable back end of their bullpen blew late leads. — Kevin Acee, San Diego Union-Tribune, 31 Aug. 2026

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