The Collaborative International Dictionary of English v.0.48:

Spiritualist \Spir"it*u*al*ist\, n.
   1. One who professes a regard for spiritual things only; one
      whose employment is of a spiritual character; an
      ecclesiastic.
      [1913 Webster]

   2. One who maintains the doctrine of spiritualism.
      [1913 Webster]

   3. One who believes in direct intercourse with departed
      spirits, through the agency of persons commonly called
      mediums, by means of physical phenomena; one who attempts
      to maintain such intercourse; a spiritist.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Spiritualist \Spir"it*u*al*ist\, a.
   Spiritualistic. --Taylor.
   [1913 Webster]

WordNet (r) 3.0 (2006):

spiritualist
    adj 1: of or relating to or connected with spiritualism [syn:
           spiritualistic, spiritualist]
    n 1: someone who serves as an intermediary between the living
         and the dead; "he consulted several mediums" [syn:
         medium, spiritualist, sensitive]

Moby Thesaurus II by Grady Ward, 1.0:

18 Moby Thesaurus words for "spiritualist":
   Berkeleian, Hegelian, Kantian, Neoplatonist, Platonist, animist,
   automatist, ecstatic, idealist, immaterialist, medium, necromancer,
   panpsychist, psychic, psychist, psychographist, spirit rapper,
   spiritist