Yes, SYNCHRONOUS is a Scrabble word!

Letter values in Scrabble US: S 1, Y 4, N 1, C 3, H 4, R 1, O 1, N 1, O 1, U 1, S 1.

Is it a valid word?

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

occurring or existing at the same time or having the same period or phase
(digital communication) pertaining to a transmission technique that requires a common clock signal (a timing reference) between the communicating devices in order to coordinate their transmissions