Yes, CRUISER is a Scrabble word!

Letter values in Scrabble US: C 3, R 1, U 1, I 1, S 1, E 1, R 1.

Is it a valid word?

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

a car in which policemen cruise the streets; equipped with radiotelephonic communications to headquarters
a large fast warship; smaller than a battleship and larger than a destroyer
a large motorboat that has a cabin and plumbing and other conveniences necessary for living on board

Also: police cruiser, patrol car, police car, prowl car, squad car, cabin cruiser, pleasure boat, pleasure craft.