A penalty called when an offensive player impedes a defender's ability to play pass defense. This can mean setting an illegal pick, where an offensive player intentionally gets in the way of another player's defender. Pass interference is also called when an offensive receiver shoves the defender away from him prior to making a play on the ball. The penalty is 10 yards from the previous line of scrimmage, and the down is replayed. Offensive pass interference cannot occur behind the line of scrimmage or after the ball has been touched following the throw.
Offensive pass interference is most often called when the offensive player makes an obvious attempt to shove the defender away from him in order to get open to catch a pass. The official will look to see if the defender could have made a play on the ball if the contact hadn't occurred. If so, the official will throw the flag. The other common form of offensive pass interference is the pick play. An offensive player will intentionally run into a defender to allow a teammate to get open. The pick is illegal, and pass interference will be called.