What does impermeable mean?
Impermeable is an adjective meaning that a substance, liquid, gas, or other material cannot pass through something. It is especially common in descriptions of protective layers, membranes, clothing, containers, and construction materials, where resistance to water, air, chemicals, or radiation may be important. The word can also describe a person or organization as being unaffected by outside pressures: an official who remains “impermeable to criticism,” for example, is not influenced by criticism. Its figurative use suggests emotional control, emotional detachment, or deliberate resistance to outside influence. The related noun “impermeability” names the quality of being impermeable. In technical writing, the expression “impermeable to” identifies the particular substance or influence that cannot pass through or affect the subject.
Not allowing a liquid, gas, or other substance to pass through; resistant to penetration.
"The coat is impermeable to wind and rain."
Often used with “to” followed by the substance that cannot pass through: impermeable to water, air, or sound.
Unaffected by or resistant to external influences, emotions, or pressures.
"Despite the scandal, the committee remained impermeable to outside pressure."
This figurative use is generally formal and often suggests deliberate emotional reserve or detachment.
From the Latin in-, meaning “not,” and permeare, meaning “to pass through,” impermeable literally means “not passable.”
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does impermeable come from?
Impermeable comes from the Latin adjective impermeabilis, meaning “not passable” or “not permeable.” It combines the prefix in-, meaning “not,” with permeare, “to pass through,” the source of English words such as permeate and permeability. English adopted the word in the 17th century, initially in contexts concerned with materials that could not be penetrated by fluids.
Related word forms
How impermeable is actually used
In technical and scientific contexts, impermeable usually describes a material or barrier that prevents passage of a specified substance. The figurative sense, impermeable to influence or criticism, is common in formal writing.
Easily confused with impermeable
Impermeable most directly describes a material that prevents substances from passing through, whereas impervious often describes someone or something unaffected by influences, emotions, or pressures.
Pervious means allowing passage through or admitting influence, while impermeable means preventing passage.