The Collaborative International Dictionary of English v.0.48:

Arbitrate \Ar"bi*trate\, v. t. [imp. & p. p. Arbitrated; p.
   pr. & vb. n. Arbitrating.] [L. arbitratus, p. p. of
   arbitrari to be a hearer or beholder of something, to make a
   decision, to give judgment, fr. arbiter. See Arbiter.]
   1. To hear and decide, as arbitrators; as, to choose to
      arbitrate a disputed case.
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   2. To decide, or determine generally. --South.
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            There shall your swords and lances arbitrate
            The swelling difference of your settled hate.
                                                  --Shak.
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