What is Touchdown ?
Touchdown is (noun) 1. the landing of a plane or spacecraft The plane veered across the runway as one of its tyres burst on touchdown. 2. (in rugby) scoring a try by touching the ground behind the opponents’ line with the ball He burst through for a touchdown between the posts. 3. US scoring a goal in American football by taking the ball over the opponents’ line He completed a pass for the winning touchdown.
source: Easier English, Student Dictionary Upper Intermediate Level