Yes, CYMOSE is a Scrabble word!

Letter values in Scrabble US: C 3, Y 4, M 3, O 1, S 1, E 1.

Is it a valid word?

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

having a usually flat-topped flower cluster in which the main and branch stems each end in a flower that opens before those below it or to its side