Source : Webster's Revised Unabridged Dictionary (1913)

Retrocession \Re`tro*ces"sion\, n. [Cf. F. r['e]trocession. See
   {Retrocede}.]
   1. The act of retroceding.

   2. The state of being retroceded, or granted back.

   3. (Med.) Metastasis of an eruption or a tumor from the
      surface to the interior of the body.