Yes, ABSOLUTER is a Scrabble word!

Letter values in Scrabble US: A 1, B 3, S 1, O 1, L 1, U 1, T 1, E 1, R 1.

Is it a valid word?

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

perfect or complete or pure
complete and without restriction or qualification; sometimes used informally as intensifiers
not limited by law
expressing finality with no implication of possible change
not capable of being violated or infringed

Also: out-and-out, right-down.