Yes, ATTITUDE is a Scrabble word!

Letter values in Scrabble US: A 1, T 1, T 1, I 1, T 1, U 1, D 2, E 1.

Is it a valid word?

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

a complex mental state involving beliefs and feelings and values and dispositions to act in certain ways
the arrangement of the body and its limbs
a theatrical pose created for effect
position of aircraft or spacecraft relative to a frame of reference (the horizon or direction of motion)

Also: mental attitude.