Yes, TOUCHDOWN is a Scrabble word!

Letter values in Scrabble US: T 1, O 1, U 1, C 3, H 4, D 2, O 1, W 4, N 1.

Is it a valid word?

TOUCHDOWN is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

a score in American football; being in possession of the ball across the opponents' goal line
a landing (as the wheels touch the landing field); especially of airplanes