Yes, TENTACLE is a Scrabble word!

Letter values in Scrabble US: T 1, E 1, N 1, T 1, A 1, C 3, L 1, E 1.

Is it a valid word?

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

something that acts like a tentacle in its ability to grasp and hold
any of various elongated tactile or prehensile flexible organs that occur on the head or near the mouth in many animals; used for feeling or grasping or locomotion