Football 101 I-L

Illegal Motion: Movement by a member of the offensive team (other than the man in motion) after the team is set and before the ball is snapped. Illegal motion is an infraction that results in a five-yard penalty.
Illegal Procedure: An instance in which the offensive team is guilty of one of several rule violations, including an illegal shift, illegal formation, or the failure to pause one second after getting set into a stance. The result is a five-yard penalty.
Incompletion: A forward pass not caught , not caught in-bounds, or intercepted.
Inside: Toward the center of the field.
Intentional Grounding: A deliberate attempt by a quarterback to throw the ball out of bounds or so that it hits the ground; the result is an incomplete forward pass. A quarterback grounds the ball to avoid being thrown for a loss. Intentional grounding can result in the loss of the down and a 15-yard penalty.
Key: To observe an opposing player closely in an attempt to determine the direction in which he is going to be moving. A running back, for example, who draws his left foot back slightly as he lines up, may be going to carry the ball to the right. Keying on the back can reveal this.
Kick: To score or attempt to score a field goal or point after touchdown by kicking the ball.
Kicking Game: A team's offensive planning that involves punting and place kicking.
Kickoff: To put the ball in play by place kicking it toward the opposing team.
Lateral, Lateral Pass: A pass thrown to the side or backward, that is, other than in the direction in which the team is attempting to advance.
Linebacker: Any of the usually three or four defensive players forming a second line-of defense behind the ends and tackles.
Line of Scrimmage: An imaginary line across the field through the forward point of the ball at which the opposing teams line up for a new play.