Yes, SELSYNS is a Scrabble word!

Letter values in Scrabble US: S 1, E 1, L 1, S 1, Y 4, N 1, S 1.

Is it a valid word?

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

a system consisting of a generator and a motor so connected that the motor will assume the same relative position as the generator; the generator and the motor are synchronized