Dictionary definition · foul
noun
- an act that violates the rules of a sport
verb
- hit a foul ball
- make impure"The industrial wastes polluted the lake"
- become or cause to become obstructed"The leaves clog our drains in the Fall"
- commit a foul; break the rules
- spot, stain, or pollute"The townspeople defiled the river by emptying raw sewage into it"
adjective
- highly offensive; arousing aversion or disgust"a disgusting smell"
- offensively malodorous"a foul odor"
- violating accepted standards or rules"a dirty fighter"
- (of a baseball) not hit between the foul lines
- (of a manuscript) defaced with changes"foul (or dirty) copy"
- characterized by obscenity"had a filthy mouth"
Source: Open English WordNet (CC BY 4.0).