Quick answer: a touchdown is a motion in which both arms extend straight up, parallel to each other, similar to the referee signal for a scored touchdown in American football - the likely source of the name.
What Does It Look Like?
Both arms extend fully straight overhead, close together and parallel rather than angled outward like a high V, hands typically in tight fists.
How the Term Is Used
"Touchdown" describes this straight-up, parallel-arm shape; its mirror opposite - the same parallel-arm shape pointed straight down at the sides - is called a low touchdown.
Where It Fits in a Routine
The touchdown motion is used throughout chants and dances, often as a strong, high-energy accent position within a motion sequence.
What Judges Look For
Judges are generally looking for fully straight, parallel arms, consistent height and angle across the team, and sharp, precise timing.
Related Motions
The touchdown is closely related to the high V, sharing the same overhead height but with the arms parallel rather than angled apart.