Yes, COELOM is a Scrabble word!

Letter values in Scrabble US: C 3, O 1, E 1, L 1, O 1, M 3.

Is it a valid word?

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

a cavity in the mesoderm of an embryo that gives rise in humans to the pleural cavity and pericardial cavity and peritoneal cavity

Not playable in Scrabble US: CELOMA.