What is Foul ?
Foul is (adj) 1. smelling or tasting unpleasant, or making an unpleasant impression What foul weather we’re having! The boss has been in a foul temper all day. A foul-smelling drain ran down the centre of the street. 2. to fall foul of to get into trouble with a person or group of people The boys fell foul of the police. She fell foul of the income tax inspectors. (noun) an action which is against the rules of a game The referee gave a free kick for a foul on the goalkeeper. Look at the action replay to see if it really was a foul. (NOTE: Do not confuse with fowl.) (verb) 1. to do something to another player which is against the rules of a game He was fouled inside the penalty box so the ref gave a penalty. 2. to foul something up to do something badly, make a mess of something, or create problems (informal.) Don’t ask John to do it he’s sure to foul it up. 3. to make something dirty, particularly by leaving excrement there Make sure that your dog does not foul the pavements.
source: Easier English, Student Dictionary Upper Intermediate Level