Yes, TRANSCENDENTAL is a Scrabble word!

Letter values in Scrabble US: T 1, R 1, A 1, N 1, S 1, C 3, E 1, N 1, D 2, E 1, N 1, T 1, A 1, L 1.

Is it a valid word?

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

existing outside of or not in accordance with nature
of or characteristic of a system of philosophy emphasizing the intuitive and spiritual above the empirical and material