The Collaborative International Dictionary of English v.0.48:

Bluff \Bluff\, v. t. [imp. & p. p. Bluffed; p. pr. & vb. n.
   Bluffing.]
   1. (Poker) To deter (an opponent) from taking the risk of
      betting on his hand of cards, as the bluffer does by
      betting heavily on his own hand although it may be of less
      value. [U. S.]
      [1913 Webster]

   2. To frighten or deter from accomplishing a purpose by
      making a show of confidence in one's strength or
      resources; as, he bluffed me off. [Colloq.]
      [1913 Webster]