befoul

To make foul; to soil; to contaminate, pollute.

These heights are a desirable retreat, for less picturesque reasons—as an escape from a compound of vile smells perpetually arising from a great harbour full of stagnant water, and befouled by the refuse of innumerable ships with all sorts of cargoes: which, in hot weather, is dreadful in the last degree.

1897, Robert Gwynneddon Davies (translator), The Sleeping Bard by Ellis Wynne, London: Simplkon, Marshall & Co., Part I, At last, what with a round of blasphemy, and the whole crowd with clay pistols belching smoke and fire and slander of their neighbours, and the floor already befouled with dregs and spittle, I feared lest viler deeds should happen, and craved to depart.

To make foul; to soil; to contaminate, pollute.

For its an ill Bird will befoule her own Nest […]

“[…] But pray what smell is that? Sure your lapdog has befoul’d himself;—let me catch hold of the nasty cur, I’ll teach him better manners.”

To stain or mar (e.g., with infamy or disgrace).

For three days Pete bore himself according to his wont, thinking to silence the evil tongues of the little world about him, and keep sweet and alive the dear name which they were waiting to befoul and destroy.

“[…] you combine a vulgar atheism and an iconoclastic desire to befoul the sacred ideas of the average man or woman, collectively scorned as the bourgeoisie——”

To entangle or run against so as to impede motion.