Yes, THRESHER is a Scrabble word!

Letter values in Scrabble US: T 1, H 4, R 1, E 1, S 1, H 4, E 1, R 1.

Is it a valid word?

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

a farm machine for separating seeds or grain from the husks and straw
large pelagic shark of warm seas with a whiplike tail used to round up small fish on which to feed

Also: threshing machine, thresher shark, fox shark, alopius vulpinus.