1.Definition: (of a baseball) not hit between the foul lines
2.Definition: (of a manuscript) defaced with changes
"Foul (or dirty) copy"
3.Definition: characterized by obscenity
4.Definition: disgustingly dirty; filled or smeared with offensive matter
"A foul pond"
5.Definition: especially of a ship's lines etc
"With its sails afoul", "A foul anchor"
6.Definition: highly offensive; arousing aversion or disgust
7.Definition: offensively malodorous
"A foul odor"
8.Definition: violating accepted standards or rules
"Used foul means to gain power"