adjective / verb

foul

FOWL/faʊl/

Offensively contaminated or dirty.

The nearby person recoils from the foul rubbish, pinching both nostrils shut.

An adult recoils and pinches nose near a foul-smelling overflowing rubbish bin, subtle odor lines.

Etymology

foulOld Englishrotten, unclean, offensive to the senses

Old English ful already described both rottenness and sensory offensiveness. The modern meaning preserves that connection: something foul is repellent through qualities such as dirtiness or a bad smell.

In context

Hello Future Me2:43

a monolithic spirit with a foul stench arrives and shishio has to clean it herself

Hard Worldbuilding vs. Soft Worldbuilding | A Study of Studio Ghibli

More examples

Oil spills foul the water and threaten nearby wildlife.
Leaking sewage has fouled the neighborhood's drinking water.
His foul language upsets the other passengers.

Forms

foul · fouls · fouled · fouling · fouler · foulest

foulness noun — The state of being disgustingly dirty.

Similar words

filthy: Emphasizes extreme dirtiness rather than contamination or offensive smells.
polluted: Emphasizes harmful contamination, especially of air, water, or land.
dirty: Means unclean without necessarily suggesting disgust or serious contamination.