The Collaborative International Dictionary of English v.0.48:

Briber \Brib"er\, n.
   1. A thief. [Obs.] --Lydgate.
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   2. One who bribes, or pays for corrupt practices.
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   3. That which bribes; a bribe.
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            His service . . . were a sufficient briber for his
            life.                                 --Shak.
      [1913 Webster]

WordNet (r) 3.0 (2006):

briber
    n 1: someone who pays (or otherwise incites) you to commit a
         wrongful act [syn: briber, suborner]