1. Chucking: Warding off an opponent who is in front of a defender by contacting him with a quick extension of arm or arms, followed by the return of arm(s) to a flexed position, thereby breaking the original contact.
2. Clipping: Throwing the body across the back of an opponent's leg or hitting him from the back below the waist while moving up from behind unless the opponent is a runner or the action is in close line play.
3. Close Line Play: The area between the positions normally occupied by the offensive tackles, extending three yards on each side of the line of scrimmage. It is legal to clip above the knee.
4. Crackback: Eligible receivers who take or move to a position more than two yards outside the tackle may not block an opponent below the waist if they then move back inside to block.
5. Dead Ball: Ball not in play.
6. Double Foul: A foul by each team during the same down.
7. Down: The period of action that starts when the ball is put in play and ends when it is dead.
8. Encroachment: When a player enters the neutral zone and makes contact with an opponent before the ball is snapped.
9. Fair Catch: An unhindered catch of a kick by a member of the receiving team who must raise one arm a full length above his head and wave his arm from side to side while the kick is in flight.
10. Foul: Any violation of a playing rule.
11. Free Kick: A kickoff or safety kick. It may be a placekick, dropkick, or punt, except a punt may not be used on a kickoff following a touchdown, successful field goal, or to begin each half or overtime period. A tee cannot be used on a fair-catch or safety kick.
12. Fumble: The loss of possession of the ball.
13. Game Clock: Scoreboard game clock.
14. Impetus: The action of a player that gives momentum to the ball.
15. Live Ball: A ball legally free kicked or snapped. It continues in play until the down ends.
16. Loose Ball: A live ball not in possession of any player.
17. Muff: The touching of a loose ball by a player in an unsuccessful attempt to obtain possession.
18. Neutral Zone: The space the length of a ball between the two scrimmage lines. The offensive team and defensive team must remain behind their end of the ball.
**Exception: The offensive player who snaps the ball.
19. Offside: A player is offside when any part of his body is beyond his scrimmage or free kick line when the ball is snapped or kicked.
20. Own Goal: The goal a team is guarding.
21. Play Clock: 40/25 second clock.
22. Pocket Area: Applies from a point two yards outside of either offensive tackle and includes the tight end if he drops off the line of scrimmage to pass protect. Pocket extends longitudinally behind the line back to offensive team's own end line.
23. Possession: When a player controls the ball throughout the act of clearly touching both feet, or any other part of his body other than his hand(s), to the ground inbounds.
24. Post-Possession Foul: A foul by the receiving team that occurs after a ball is legally kicked from scrimmage prior to possession changing. The ball must cross the line of scrimmage and the receiving team must retain possession of the kicked ball.
25. Punt: A kick made when a player drops the ball and kicks it while it is in flight.
26. Safety: The situation in which the ball is dead on or behind a team's own goal if the impetus comes from a player on that team. Two points are scored for the opposing team.
27. Shift: The movement of two or more offensive players at the same time before the snap.
28. Striking: The act of swinging, clubbing, or propelling the arm or forearm in contacting an opponent.
29. Sudden Death: The continuation of a tied game into sudden death overtime in which the team scoring first (by safety, field goal, or touchdown) wins.
30. Touchback: When a ball is dead on or behind a team's own goal line, provided the impetus came from an opponent and provided it is not a touchdown or a missed field goal.
31. Touchdown: When any part of the ball, legally in possession of a player inbounds, breaks the plane of the opponent's goal line, provided it is not a touchback.
32. Unsportsmanlike Conduct: Any act contrary to the generally understood principles of sportsmanship.