The Collaborative International Dictionary of English v.0.48:

Consociation \Con*so`ci*a"tion\, n. [L. consociatio.]
   1. Intimate union; fellowship; alliance; companionship;
      confederation; association; intimacy.
      [1913 Webster]

            A friendly consociation with your kindred elements.
                                                  --Warburton.
      [1913 Webster]

   2. A voluntary and permanent council or union of neighboring
      Congregational churches, for mutual advice and cooperation
      in ecclesiastical matters; a meeting of pastors and
      delegates from churches thus united.
      [1913 Webster]

   Note: In Connecticut some of the Congregational churhes are
         associated in consociations and the others in
         conferences.
         [1913 Webster]