The Collaborative International Dictionary of English v.0.48:

Ritualism \Rit"u*al*ism\, n. [Cf. F. ritualisme.]
   1. A system founded upon a ritual or prescribed form of
      religious worship; adherence to, or observance of, a
      ritual.
      [1913 Webster]

   2. Specifically :
      (a) The principles and practices of those in the Church of
          England, who in the development of the Oxford
          movement, so-called, have insisted upon a return to
          the use in church services of the symbolic ornaments
          (altar cloths, encharistic vestments, candles, etc.)
          that were sanctioned in the second year of Edward VI.,
          and never, as they maintain, forbidden by competennt
          authority, although generally disused. Schaff-Herzog
          Encyc.
      (b) Also, the principles and practices of those in the
          Protestant Episcopal Church who sympathize with this
          party in the Church of England.
          [1913 Webster]

WordNet (r) 3.0 (2006):

ritualism
    n 1: the study of religious or magical rites and ceremonies
    2: exaggerated emphasis on the importance of rites or
       ritualistic forms in worship

The Devil's Dictionary (1881-1906):

RITUALISM, n.  A Dutch Garden of God where He may walk in rectilinear
freedom, keeping off the grass.