The Collaborative International Dictionary of English v.0.48:

Processional \Pro*ces"sion*al\, a.
   Of or pertaining to a procession; consisting in a procession.
   [1913 Webster]

         The processional services became more frequent.
                                                  --Milman.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Processional \Pro*ces"sion*al\, n. [F. processionnal, LL.
   processionale.]
   [1913 Webster]
   1. (R. C. Ch.) A service book relating to ecclesiastical
      processions. --J. Gregory.
      [1913 Webster]

   2. A hymn, or other selection, sung during a church
      procession; as, the processional was the 202d hymn.
      [1913 Webster]

WordNet (r) 3.0 (2006):

processional
    adj 1: intended for use in a procession; "processional music";
           "processional cross"
    2: of or relating to or characteristic of a procession; "in good
       processional order"
    n 1: religious music used in a procession [syn: processional,
         prosodion]

Moby Thesaurus II by Grady Ward, 1.0:

24 Moby Thesaurus words for "processional":
   agape, asperges, aspersion, auricular confession, bar mitzvah,
   bas mitzvah, celebration, circumcision, confession, confirmation,
   high celebration, incense, invocation, invocation of saints,
   kiss of peace, lesser litany, litany, love feast, lustration, pax,
   reciting the rosary, telling of beads, the confessional,
   the confessionary