Befoul Definition

bĭ-foul
befouled, befouls
verb
befouled, befouls
To make dirty; soil.
American Heritage
To make filthy; dirty; soil.
Webster's New World
To cast aspersions upon; speak badly of.
American Heritage
To cast aspersions on; slander.
Webster's New World

To make foul; to soil.

Wiktionary