The result of a play (usually a kickoff or punt) in which the ball passes out the back of the end zone or a team otherwise gains possession of the ball in their own end zone
The ball sailed into the end zone for a touchback and the Eagles had possession on the 20-yard line.
(American football) a play in which the opposing team has kicked the football into your end zone
The act of touching the football down by a player behind his own goal line when it received its last impulse from an opponent; distinguished from safety touchdown