Real Dictionary

bluff
If you describe someone as bluff, you mean that they have a very direct way of speaking and behaving.
countable noun: A bluff is a steep cliff or bank, especially by a river or the sea.
variable noun: A bluff is an attempt to make someone believe that you will do something when you do not really intend to do it.
verb: If you bluff, you make someone believe that you will do something when you do not really intend to do it, or that you know something when you do not really know it.

bluff in American English 1
the act or practice of bluffing
to mislead or seek to mislead (a person) by a false, bold front
adjective: good-naturedly direct, blunt, or frank; heartily outspoken
noun: a cliff, headland, or hill with a broad, steep face

bluff in American English 2
a high, steep, broad-faced bank or cliff
having, or ascending steeply with, a broad, flat front
intransitive verb: to mislead someone by presenting a bold, strong, or self-confident front
noun: an act or instance or the practice of bluffing
transitive verb: to mislead by a display of strength, self-confidence, or the like

bluff in British English 1
noun: deliberate deception intended to create the impression of a stronger position or greater resources than one actually has
verb: to pretend to be confident about an uncertain issue or to have undisclosed resources, in order to influence or deter (someone)

bluff in British English 2
adjective: good-naturedly frank and hearty
noun: a steep promontory, bank, or cliff, esp one formed by river erosion on the outside bend of a meander