Yes, PROCESSION is a Scrabble word!

Letter values in Scrabble US: P 3, R 1, O 1, C 3, E 1, S 1, S 1, I 1, O 1, N 1.

Is it a valid word?

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

(theology) the origination of the Holy Spirit at Pentecost
the group action of a collection of people or animals or vehicles moving ahead in more or less regular formation
the act of moving forward (as toward a goal)

Also: forward motion, onward motion.