Yes, TRUNKS is a Scrabble word!

Letter values in Scrabble US: T 1, R 1, U 1, N 1, K 5, S 1.

Is it a valid word?

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

trousers that end at or above the knee
the main stem of a tree; usually covered with bark; the bole is usually the part that is commercially useful for lumber
luggage consisting of a large strong case used when traveling or for storage
the body excluding the head and neck and limbs
compartment in an automobile that carries luggage or shopping or tools
a long flexible snout as of an elephant

Also: short pants, tree trunk, luggage compartment, automobile trunk.