The Collaborative International Dictionary of English v.0.48:

payoff \payoff\ n.
   1. profit or gain from an action; -- used broadly; as, lots
      of effort with little payoff.
      [PJC]

   2. retribution, payback.
      [PJC]

   3. The act of giving or receiving money or other valuable
      consideration as a bribe.

   Syn: bribe.
        [PJC]

   4. The money or item given as a bribe.
      [PJC]

   5. same as compensation 2.

   Syn: compensation, remuneration, recompense.
        [PJC]

   6. The climax or final result of an event or endeavor; the
      denoument of a narrative.
      [PJC]

WordNet (r) 3.0 (2006):

payoff
    n 1: the final payment of a debt [syn: payoff, final
         payment]
    2: payment made to a person in a position of trust to corrupt
       his judgment [syn: bribe, payoff]
    3: the income or profit arising from such transactions as the
       sale of land or other property; "the average return was about
       5%" [syn: return, issue, take, takings, proceeds,
       yield, payoff]
    4: a recompense for worthy acts or retribution for wrongdoing;
       "the wages of sin is death"; "virtue is its own reward" [syn:
       wages, reward, payoff]

Moby Thesaurus II by Grady Ward, 1.0:

116 Moby Thesaurus words for "payoff":
   Z, acquitment, acquittal, acquittance, amortization, amortizement,
   apodosis, binder, bitter end, boodle, bribe, bribe money, cash,
   cash payment, catastrophe, ceasing, cessation, clearance, climax,
   coda, completion, conclusion, consummation, crack of doom,
   culmination, curtain, curtains, death, debt service, decease,
   defrayal, defrayment, denouement, deposit, destination, destiny,
   disbursal, discharge, doling out, doom, down payment, earnest,
   earnest money, effect, end, end point, end result, ending, envoi,
   epilogue, eschatology, expiration, fate, final result,
   final solution, final twitch, final words, finale, finality, finis,
   finish, goal, gratification, gratuity, hire purchase,
   hire purchase plan, hush money, installment, installment plan,
   interest payment, izzard, last, last act, last breath, last gasp,
   last things, last trumpet, last words, latter end, liquidation,
   monthly payments, never-never, omega, paying, paying off,
   paying out, paying up, payment, payment in kind, payola, period,
   peroration, prepayment, protection, quarterly payments, quietus,
   quittance, regular payments, remittance, resolution, resting place,
   retirement, satisfaction, settlement, sinking-fund payment, sop,
   spot cash, stoppage, stopping place, swan song, term, terminal,
   termination, terminus, weekly payments, windup