The Collaborative International Dictionary of English v.0.48:

fascism \fasc"ism\ (f[a^]sh"[i^]z'm) n.
   1. a political theory advocating an authoritarian
      hierarchical government; -- opposed to democracy and
      liberalism.
      [WordNet 1.5]

   2. an authoritarian system of government under absolute
      control of a single dictator, allowing no political
      opposition, forcibly suppressing dissent, and rigidly
      controlling most industrial and economic activities. Such
      regimes usually try to achieve popularity by a strongly
      nationalistic appeal, often mixed with racism.
      [PJC]

   3. Specifically, the Fascist movement led by Benito Mussolini
      in Italy from 1922 to 1943.
      [PJC]

   4. broadly, a tendency toward or support of a strongly
      authoritarian or dictatorial control of government or
      other organizations; -- often used pejoratively in this
      sense.
      [PJC]

WordNet (r) 3.0 (2006):

fascism
    n 1: a political theory advocating an authoritarian hierarchical
         government (as opposed to democracy or liberalism)