Yes, POUNDERS is a Scrabble word!

Letter values in Scrabble US: P 3, O 1, U 1, N 1, D 2, E 1, R 1, S 1.

Is it a valid word?

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

(used only in combination) something weighing a given number of pounds
a heavy tool of stone or iron (usually with a flat base and a handle) that is used to grind and mix material (as grain or drugs or pigments) against a slab of stone