a play in which the ball is downed after having been kicked into the end zone by the opposing team or having been recovered or intercepted there, or in which it has been kicked beyond the end zone.
At the end of a fifteen-minute scrimmage the varsity had forced its opponents to two touchdowns and a touchback.
British Dictionary definitions for touchback
touchback
/ˈtʌtʃˌbæk/
noun
1.
(American football) a play in which the ball is put down by a player behind his own goal line when the ball has been put across the goal line by an opponent Compare safety (sense 4b)