be·foul \bə̇, bē+\transitive verb (-ed/-ing/-s) Etymology: Middle English befoulen, alteration (influenced by foul) of befilen to befoul, from Old English befȳlan, from be- + fȳlan to foul — more at file 1.: to make foul with or as if with dirt or filth < a building befouled with soot > < mudslinging befouled his speeches > 2. a.: slander, calumniate < befouling his reputation > b.: disgrace, blacken, denigrate < scandals that befouled the administration >