The Collaborative International Dictionary of English v.0.48:

Exordial \Ex*or"di*al\ ([e^]gz*[^o]r"d[i^]*al), a.
   Pertaining to the exordium of a discourse: introductory.
   [1913 Webster]

         The exordial paragraph of the second epistle. --I.
                                                  Taylor.
   [1913 Webster]