The Collaborative International Dictionary of English v.0.48:

Dimissory \Dim"is*so*ry\ (?; 277), a. [L. dimissorius: cf. F.
   dimissoire. See Dimit.]
   Sending away; dismissing to another jurisdiction; granting
   leave to depart.
   [1913 Webster]

   Letters dimissory (Eccl.), letters given by a bishop
      dismissing a person who is removing into another diocese,
      and recommending him for reception there. --Hook.
      [1913 Webster]