The Collaborative International Dictionary of English v.0.48:

Ritual \Rit"u*al\, a.[L. ritualis, fr. ritus a rite: cf. F.
   rituel.]
   Of or pertaining to rites or ritual; as, ritual service or
   sacrifices; the ritual law.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Ritual \Rit"u*al\, n. [Cf. F. rituel.]
   1. A prescribed form of performing divine service in a
      particular church or communion; as, the Jewish ritual.
      [1913 Webster]

   2. Hence, the code of ceremonies observed by an organization;
      as, the ritual of the freemasons.
      [1913 Webster]

   3. A book containing the rites to be observed.
      [1913 Webster]

WordNet (r) 3.0 (2006):

ritual
    adj 1: of or relating to or characteristic of religious rituals;
           "ritual killing"
    2: of or relating to or employed in social rites or rituals; "a
       ritual dance of Haiti"; "sedate little colonial tribe with
       its ritual tea parties"- Nadine Gordimer
    n 1: any customary observance or practice [syn: ritual,
         rite]
    2: the prescribed procedure for conducting religious ceremonies
    3: stereotyped behavior