Yes, SLOUGHS is a Scrabble word!

Letter values in Scrabble US: S 1, L 1, O 1, U 1, G 2, H 4, S 1.

Is it a valid word?

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

necrotic tissue; a mortified or gangrenous part or mass
a hollow filled with mud
a stagnant swamp (especially as part of a bayou)
any outer covering that can be shed or cast off (such as the cast-off skin of a snake)

Not playable in Scrabble US: SPHACELUS.