Yes, MAXIMS is a Scrabble word!

Letter values in Scrabble US: M 3, A 1, X 8, I 1, M 3, S 1.

Is it a valid word?

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

a saying that is widely accepted on its own merits
English inventor (born in the United States) who invented the Maxim gun that was used in World War I (1840-1916)

Also: sir hiram stevens maxim.