Yes, COMMUNION is a Scrabble word!

Letter values in Scrabble US: C 3, O 1, M 3, M 3, U 1, N 1, I 1, O 1, N 1.

Is it a valid word?

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

the act of participating in the celebration of the Eucharist
sharing thoughts and feelings
(Christianity) a group of Christians with a common religious faith who practice the same rites

Also: holy communion, sacramental manduction.

Not playable in Scrabble US: MANDUCTION.