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]