Yes, CUSHION is a Scrabble word!

Letter values in Scrabble US: C 3, U 1, S 1, H 4, I 1, O 1, N 1.

Is it a valid word?

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

a mechanical damper; absorbs energy of sudden impulses
the layer of air that supports a hovercraft or similar vehicle
a soft bag filled with air or a mass of padding such as feathers or foam rubber etc.

Also: shock absorber.