Yes, POCKETKNIFE is a Scrabble word!

Letter values in Scrabble US: P 3, O 1, C 3, K 5, E 1, T 1, K 5, N 1, I 1, F 4, E 1.

Is it a valid word?

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

a knife with a blade that folds into the handle; suitable for carrying in the pocket

Also: pocket knife.