What is "letters dimissory"

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

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