Sentence:  The <WSD>off-side rule</WSD> in football states that no player may be closer to his opponents' goal than his last two opponents (usually a defender and the goalkeeper) and the ball at the time the ball is kicked forwards towards him. 
Meaning of the word marked with <WSD> tags:  The prohibition of teammates closer to the opponents' goal than the person kicking or throwing the ball unless there are three opponents at least as close to their goal line.