The Collaborative International Dictionary of English v.0.48:

Symbolism \Sym"bol*ism\, n.
   1. The act of symbolizing, or the state of being symbolized;
      as, symbolism in Christian art is the representation of
      truth, virtues, vices, etc., by emblematic colors, signs,
      and forms.
      [1913 Webster]

   2. A system of symbols or representations.
      [1913 Webster]

   3. (Chem.)
      (a) The practice of using symbols, or the system of
          notation developed thereby.
      (b) A combining together of parts or ingredients. [Obs.]
          [1913 Webster]

   4. (Theol.) The science of creeds; symbolics.
      [1913 Webster]

WordNet (r) 3.0 (2006):

symbolism
    n 1: a system of symbols and symbolic representations
    2: the practice of investing things with symbolic meaning [syn:
       symbolism, symbolization, symbolisation]
    3: an artistic movement in the late 19th century that tried to
       express abstract or mystical ideas through the symbolic use
       of images