befoul

UK: /bɪˈfaʊl/ US: (bi foul′)

WordReference Random House Unabridged Dictionary of American English © 2025

be•foul  (bi foul′), v.t. 

1. to make dirty or filthy;
   soil;
   defile;
   sully:
   a bird that befouls its own nest.

• Middle English bi-foulen. See be-, foul 1275–1325

be•foul′er, n. 
be•foul′ment, n. 

Collins Concise English Dictionary © HarperCollins Publishers::

befoul / bɪˈfaʊl/ verb

1. (transitive) to make dirty or foul; soil; defile