Definition of bluff:
a high, steep bank, as by a river or the sea, or beside a ravine or plain; a cliff with a broad face; an act of bluffing; an expression of self-confidence
for the purpose of intimidation
; as, that is only bluff, or a bluff
"john's bet was a bluff, he bet without even so much as a pair."
having a broad, flattened front; as, the bluff bows of a ship; rising steeply with a flat or rounded front
to make a bluff
"john bluffed by betting without even a pair."