Yes, SPITBALL is a Scrabble word!

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

Is it a valid word?

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

a projectile made by chewing a piece of paper and shaping it into a sphere
an illegal pitch in which a foreign substance (spit or Vaseline) is applied to the ball by the pitcher before he throws it