Source : Webster's Revised Unabridged Dictionary (1913)

Go-between \Go"-be*tween`\, n.
   An intermediate agent; a broker; a procurer; -- usually in a
   disparaging sense. --Shak.

Source : WordNet®

go-between
     n : a negotiator who acts as a link between parties [syn: {mediator},
          {intermediator}, {intermediary}, {intercessor}]