Yes, POSSIBILITY is a Scrabble word!

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

Is it a valid word?

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

a future prospect or potential
capability of existing or happening or being true
a tentative insight into the natural world; a concept that is not yet verified but that if true would explain certain facts or phenomena
a possible alternative

Also: possible action.

Not playable in Scrabble US: POSSIBLENESS.