adjective

impervious

im-PUR-vee-us/ɪmˈpɜːrviəs/

Not permitting penetration by an outside substance.

The protective coating makes the fabric impervious to rain.

A waterproof sheet stretched over a shallow frame blocks a stream of water: water beads and runs off its upper surface while a white tissue directly beneath remains completely dry.

Etymology

imLatinnot

+perLatinthrough

+viousLatinroad, way

“Not,” “through,” and “road” give the image of no way through. The sense of blocking passage also extends to being unaffected by something, as though its influence cannot get through.

In context

Enhanced Public Domain199:32

before dark and opaque bodies had surrounded me impervious to my touch or sight

1800s Fiction Audiobook: Mary Shelley - Frankenstein

More examples

We need gloves that are impervious to this solvent.
The container has an impervious lining that keeps moisture out.
Water collects above a layer of rock impervious to water.

Forms

impervious

imperviousness noun — The quality of preventing substances from penetrating.

Similar words

impermeable: Specifically prevents liquids or gases from passing through a material.
impenetrable: Blocks entry or passage, not necessarily just liquids or gases.
waterproof: Specifically prevents water from entering, rather than other substances.