The Collaborative International Dictionary of English v.0.48:

Consubstantiation \Con`sub*stan`ti*a"tion\ (?; 106), n.
   1. An identity or union of substance.
      [1913 Webster]

   2. (Theol.) The actual, substantial presence of the body of
      Christ with the bread and wine of the sacrament of the
      Lord's Supper; impanation; -- opposed to
      transubstantiation.
      [1913 Webster]

   Note: This view, held by Luther himself, was called
         consubstantiation by non Lutheran writers in
         contradistinction to transsubstantiation, the Catholic
         view.
         [1913 Webster]

WordNet (r) 3.0 (2006):

consubstantiation
    n 1: the doctrine of the High Anglican Church that after the
         consecration of the Eucharist the substance of the body and
         blood of Christ coexists with the substance of the
         consecrated bread and wine