The Collaborative International Dictionary of English v.0.48:

Ceremonial \Cer`e*mo"ni*al\, n.
   1. A system of rules and ceremonies, enjoined by law, or
      established by custom, in religious worship, social
      intercourse, or the courts of princes; outward form.
      [1913 Webster]

            The gorgeous ceremonial of the Burgundian court.
                                                  --Prescott.
      [1913 Webster]

   2. The order for rites and forms in the Roman Catholic
      church, or the book containing the rules prescribed to be
      observed on solemn occasions.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Ceremonial \Cer`e*mo"ni*al\, a. [L. caerimonialis: cf. F.
   c['e]rimonial. See Ceremony.]
   1. Relating to ceremony, or external rite; ritual; according
      to the forms of established rites.
      [1913 Webster]

            Ceremonial observances and outward show. --Hallam.
      [1913 Webster]

   2. Observant of forms; ceremonious.

   Note: [In this sense ceremonious is now preferred.] --Donne.
         [1913 Webster]

               He moves in the dull ceremonial track. --Druden.
         [1913 Webster]

WordNet (r) 3.0 (2006):

ceremonial
    adj 1: marked by pomp or ceremony or formality; "a ceremonial
           occasion"; "ceremonial garb"
    n 1: a formal event performed on a special occasion; "a ceremony
         commemorating Pearl Harbor" [syn: ceremony, ceremonial,
         ceremonial occasion, observance]

Moby Thesaurus II by Grady Ward, 1.0:

95 Moby Thesaurus words for "ceremonial":
   High-Church, august, baccalaureate service, baptismal, buckram,
   celebration, celebratory, ceremonious, ceremoniousness, ceremony,
   commemorative, commencement, conventional, convocation, courtly,
   decorous, dignified, dignity, duty, empty formality, eucharistic,
   exercise, exercises, extrinsicality, form, form of worship, formal,
   formality, formalization, formula, formular, formulary, function,
   graduation, graduation exercises, gravity, hieratic, holy rite,
   impersonality, imposing, inaugural, inauguration, initiation,
   institution, liturgic, liturgical, liturgistic, liturgy, lofty,
   mannered, mode of worship, mummery, mystery, observance, office,
   order of worship, ordinance, paschal, performance, pomp, pomposity,
   pompous, practice, prescribed form, primness, religious ceremony,
   rigid, rigidness, rite, rite de passage, rite of passage, ritual,
   ritual observance, ritualistic, rituality, sacerdotal, sacrament,
   sacramental, sacramentarian, service, set, solemn, solemnity,
   solemnization, starchiness, starchy, stately, stiff, stiffness,
   stiltedness, studied, stylization, stylized, weight,
   well-mannered