Yes, BLUFF is a Scrabble word!

Letter values in Scrabble US: B 3, L 1, U 1, F 4, F 4.

Is it a valid word?

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

a high steep bank (usually formed by river erosion)
pretense that your position is stronger than it really is
the act of bluffing in poker; deception by a false show of confidence in the strength of your cards

deceive an opponent by a bold bet on an inferior hand with the result that the opponent withdraws a winning hand
frighten someone by pretending to be stronger than one really is

BLUFF was the Wordle answer on July 30, 2022 (#406). Stuck on today’s? Use the Wordle helper.

Also: four flush, bluff out.