Yes, COMA is a Scrabble word!

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

Is it a valid word?

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

a state of deep and often prolonged unconsciousness; usually the result of disease or injury
(botany) a usually terminal tuft of bracts (as in the pineapple) or tuft of hairs (especially on certain seeds)
(astronomy) the luminous cloud of particles surrounding the frozen nucleus of a comet; forms as the comet approaches the sun and is warmed

Not playable in Scrabble US: COMATOSENESS.