Yes, WITHDRAWAL is a Scrabble word!

Letter values in Scrabble US: W 4, I 1, T 1, H 4, D 2, R 1, A 1, W 4, A 1, L 1.

Is it a valid word?

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

a retraction of a previously held position
the act of taking out money or other capital
the act of withdrawing
avoiding emotional involvement
the act of withdrawing blood, tumors, etc.
the act of ceasing to participate in an activity
a method of birth control in which coitus is initiated but the penis is deliberately withdrawn before ejaculation
formal separation from an alliance or federation
the termination of drug taking

Also: climb-down, coitus interruptus, withdrawal method, pulling out, drug withdrawal.

Not playable in Scrabble US: BACKDOWN.