A term for any moment when play has stopped. A dead ball cannot be advanced by either team, and is dead until the ball is placed at the correct place on the field to begin the next play and signaled for play by an official. The ball cannot be snapped on a dead ball, and there should be no contact between players during a dead ball. Certain penalties only apply during dead ball situations.
The dead ball is the primary indicator when a play has stopped. The referee will blow the whistle, and at that point contact should cease and players should head to their respective sides of the line of scrimmage to prepare for the next play. The official will then place the ball at the proper point so that the next play can start. Once the ball has been placed, the offense is free to begin the next play. Certain penalties are considered "dead ball fouls", which means they are assessed after the conclusion of the play.