Yes, STYPSISES is a Scrabble word!

Letter values in Scrabble US: S 1, T 1, Y 4, P 3, S 1, I 1, S 1, E 1, S 1.

Is it a valid word?

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

the ability to contract or draw together soft body tissues to check blood flow or restrict secretion of fluids