The Collaborative International Dictionary of English v.0.48:

Recessional \Re*ces"sion*al\, a.
   Of or pertaining to recession or withdrawal.
   [1913 Webster]

   Recessional hymn, a hymn sung in a procession returning
      from the choir to the robing room; a recessional.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

recessional \re*ces"sion*al\ (r[-e]*s[e^]sh"[u^]n*al), n.
   a hymn or other piece of music sung or played while a church
   congregation is leaving a service, or a choir is returning to
   the cloak room; a recessional hymn.
   [PJC]

WordNet (r) 3.0 (2006):

recessional
    adj 1: of or relating to receding
    n 1: the withdrawal of the clergy and choir from the chancel to
         the vestry at the end of a church service [syn:
         recession, recessional]
    2: a hymn that is sung at the end of a service as the clergy and
       choir withdraw