Yes, LOGGERHEAD is a Scrabble word!

Letter values in Scrabble US: L 1, O 1, G 2, G 2, E 1, R 1, H 4, E 1, A 1, D 2.

Is it a valid word?

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

a stupid person; these words are used to express a low opinion of someone's intelligence
very large carnivorous sea turtle; wide-ranging in warm open seas

Also: loggerhead turtle, caretta caretta.

Not playable in Scrabble US: MUTTONHEAD, DUMBASS, FUCKHEAD.