Definition of foul:
covered with, or containing, extraneous matter which is injurious, noxious, offensive, or obstructive; filthy; dirty; not clean; polluted; nasty; defiled; as, a foul cloth; foul hands; a foul chimney; foul air; a ship's bottom is foul when overgrown with barnacles; a gun becomes foul from repeated firing; a well is foul with polluted water; scurrilous; obscene or profane; abusive; as, foul words; foul language
"cap'n, she's all fouled up."
"he's fouled her diapers."
the act of making contact with an opposing player in order to gain advantage; a foul ball
, a ball which has been hit outside of the base lines
"jones hit a foul up over the screen."