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

• dense
• impervious
• impenetrable
• impassable
• thick
• close
• sturdy

Examples of impermeable in a Sentence

an impermeable layer of rock

a fabric impermeable to moisture

Recent Examples on the Web

The company says the finalized Bio foil provides the full and appropriate level of impermeable barrier protection and odorless performance. —New Atlas, 9 Oct. 2025

Chocolate brown stripes punctuate a light charcoal gray background, and the low-pile weave made from recycled polyester gives it an impermeable, easy-to-clean surface. —Julia Harrison, Architectural Digest, 6 Oct. 2025

Typically, these formations have porous rock layers overlaid by impermeable rock that blocks upward movement. —Tejasri Gururaj, Interesting Engineering, 3 Oct. 2025

Which means the bigger the economy, the greater the means to erect an impermeable national defense system. —John Tamny, Forbes.com, 12 Sep. 2025

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