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):

bunco
    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]
    v 1: deprive of by deceit; "He swindled me out of my
         inheritance"; "She defrauded the customers who trusted
         her"; "the cashier gypped me when he gave me too little
         change" [syn: victimize, swindle, rook, goldbrick,
         nobble, diddle, bunco, defraud, scam, mulct,
         gyp, gip, hornswoggle, short-change, con]

Moby Thesaurus II by Grady Ward, 1.0:

26 Moby Thesaurus words for "bunco":
   ballot-box stuffing, cardsharping, cheat, cheating, cozenage,
   diddle, diddling, dishonesty, dodge, fishy transaction, flam,
   flimflam, fraud, fraudulence, fraudulency, gerrymandering, graft,
   grift, gyp, gyp joint, illicit business, imposition, imposture,
   racket, scam, swindle