adjective / verb
foul
FOWL/faʊl/
Offensively contaminated or dirty.
The nearby person recoils from the foul rubbish, pinching both nostrils shut.

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