The Collaborative International Dictionary of English v.0.48:

Mediate \Me"di*ate\, v. i. [imp. & p. p. Mediated; p. pr. &
   vb. n. Mediating.] [LL. mediatus, p. p. of mediare to
   mediate. See Mediate, a.]
   [1913 Webster]
   1. To be in the middle, or between two; to intervene. [R.]
      [1913 Webster]

   2. To interpose between parties, as the equal friend of each,
      esp. for the purpose of effecting a reconciliation or
      agreement; as, to mediate between nations.
      [1913 Webster]

WordNet (r) 3.0 (2006):

mediated
    adj 1: acting or brought about through an intervening agency;
           "the mediated settlement brought satisfaction to both
           sides"