The Collaborative International Dictionary of English v.0.48:

Occultism \Oc*cult"ism\, n.
   1. A certain Oriental system of theosophy. --A. P. Sinnett.
      [1913 Webster]

   2. Belief in occult powers or in supernatural forces other
      than the God of traditional religions, such as in magic,
      necromancy, alchemy, and astrology.
      [PJC]

   3. The study and alleged use of supernatural agencies as in
      magic, astrology, witchcraft, alchemy, necromancy,
      spiritualism (communication with the dead), and
      fortune-telling.
      [PJC]

WordNet (r) 3.0 (2006):

occultism
    n 1: the study of the supernatural
    2: a belief in supernatural powers and the possibility of
       bringing them under human control

Moby Thesaurus II by Grady Ward, 1.0:

27 Moby Thesaurus words for "occultism":
   bodilessness, ghostliness, immateriality, immaterialness,
   impalpability, imponderability, incorporeality, incorporeity,
   inextension, intangibility, nonexteriority, occult phenomena,
   otherworldliness, psychical research, psychicism, psychics,
   psychism, shadowiness, spirit world, spirituality, spirituousness,
   supernaturalism, the occult, unearthliness, unsubstantiality,
   unsubstantialness, unworldliness