The Collaborative International Dictionary of English v.0.48:

Bunko \Bun"ko\, v. t. [imp. & p. p. Bunkoed; p. pr. & vb. n.
   Bunkoing.]
   To swindle by a bunko game or scheme; to cheat or victimize
   in any similar way, as by a confidence game, passing a bad
   check, etc.
   [Webster 1913 Suppl.]

   Bunko steerer, a person employed as a decoy in bunko.
      [Slang, U.S.]
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Bunko \Bun"ko\, n. [Sf. Sp. banco bank, banca a sort of game at
   cards. Cf. Bank (in the commercial sense).]
   A kind of swindling game or scheme, originally by means of
   cards or by a sham lottery, but now used for any swindling
   tactic. [Written also bunco.]
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Bunco \Bun"co\, n.
   see bunko. [Written also bunko.]
   [PJC] Buncombe

WordNet (r) 3.0 (2006):

bunko
    n 1: a swindle in which you cheat at gambling or persuade a
         person to buy worthless property [syn: bunco, bunco
         game, bunko, bunko game, con, confidence trick,
         confidence game, con game, gyp, hustle, sting,
         flimflam]