The Collaborative International Dictionary of English v.0.48:

Superstition \Su`per*sti"tion\, n. [F. superstition, L.
   superstitio, originally, a standing still over or by a thing;
   hence, amazement, wonder, dread, especially of the divine or
   supernatural, fr. superstare to stand over; super over +
   stare to stand. See Super-, and Stand.]
   1. An excessive reverence for, or fear of, that which is
      unknown or mysterious.
      [1913 Webster]

   2. An ignorant or irrational worship of the Supreme Deity;
      excessive exactness or rigor in religious opinions or
      practice; extreme and unnecessary scruples in the
      observance of religious rites not commanded, or of points
      of minor importance; also, a rite or practice proceeding
      from excess of sculptures in religion.
      [1913 Webster]

            And the truth
            With superstitions and traditions taint. --Milton.
      [1913 Webster]

   3. The worship of a false god or gods; false religion;
      religious veneration for objects.
      [1913 Webster]

            [The accusers] had certain questions against him of
            their own superstition.               --Acts xxv.
                                                  19.
      [1913 Webster]

   4. Belief in the direct agency of superior powers in certain
      extraordinary or singular events, or in magic, omens,
      prognostics, or the like.
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   5. Excessive nicety; scrupulous exactness.
      [1913 Webster]

   Syn: Fanaticism.

   Usage: Superstition, Fanaticism. Superstition springs
          from religious feeling misdirected or unenlightened.
          Fanaticism arises from this same feeling in a state of
          high-wrought and self-confident excitement. The former
          leads in some cases to excessive rigor in religious
          opinions or practice; in others, to unfounded belief
          in extraordinary events or in charms, omens, and
          prognostics, hence producing weak fears, or excessive
          scrupulosity as to outward observances. The latter
          gives rise to an utter disregard of reason under the
          false assumption of enjoying a guidance directly
          inspired. Fanaticism has a secondary sense as applied
          to politics, etc., which corresponds to the primary.
          [1913 Webster]

WordNet (r) 3.0 (2006):

superstition
    n 1: an irrational belief arising from ignorance or fear [syn:
         superstition, superstitious notion]