Etymology: Middle English, from Old English fūl; akin to Old High German fūl rotten, Latin pus pus, putēre to stink, Greek pyon pus
Date: before 12th century
1 a: offensive to the senses :loathsomeb: filled or covered with offensive matter 2: full of dirt or mud 3 a: morally or spiritually odious :detestable<a foul crime>b: notably unpleasant or distressing :wretched, horrid<in a foul mood> 4:obscene, abusive<foul language> 5 a: being wet and stormy b: obstructive to navigation <a foul tide> 6dialect British:homely, ugly 7 a:treacherous, dishonorable<fair means or foul>b: constituting an infringement of rules in a game or sport <a foul blow in boxing> 8: containing marked-up corrections <a foul manuscript><foul proofs> 9: encrusted, clogged, or choked with a foreign substance <the chimney was foul and smoked badly> 10: being odorous and impure :polluted<foul air> 11: placed in a situation that impedes physical movement :entangled 12: being outside the foul lines in baseball