The term 'of scrimmage' in American football refers to the LINE of scrimmage, which is the imaginary LINE that marks the beginning of a play. It is the point at which the ball is placed by the center before the snap. The LINE of scrimmage is determined by the position of the ball relative to the offensive team's LINE of scrimmage. The offensive team must have seven players on the LINE of scrimmage at the start of the play. The defensive team must have at least four players on the LINE of scrimmage. The LINE of scrimmage is an important part of the game as it determines the area in which the offense and defense can move.