Yes, SPIRITUALISM is a Scrabble word!

Letter values in Scrabble US: S 1, P 3, I 1, R 1, I 1, T 1, U 1, A 1, L 1, I 1, S 1, M 3.

Is it a valid word?

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

(theology) any doctrine that asserts the separate existence of God
the belief that the spirits of dead people can communicate with people who are still alive (especially via a medium)
concern with things of the spirit

Also: otherworldliness.