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)

Moby Thesaurus II by Grady Ward, 1.0:

72 Moby Thesaurus words for "fascism":
   Jim Crow, Jim Crow law, Nazism, anti-Semitism, apartheid,
   argumentum baculinum, big stick, black power, black supremacy,
   centralism, chauvinism, class consciousness, class distinction,
   class hatred, class prejudice, class war, collectivism, color bar,
   color line, communism, constitutionalism, democratism, despotism,
   discrimination, domination, domineering, federalism, feudalism,
   feudality, governmentalism, heavy hand, high hand, imperialism,
   iron boot, iron hand, iron heel, know-nothingism, male chauvinist,
   minority prejudice, monarchism, national socialism, neofascism,
   oppression, parliamentarianism, parliamentarism, pluralism,
   political principles, race hatred, race prejudice, race snobbery,
   racial discrimination, racialism, racism, red-baiting,
   reign of terror, republicanism, royalism, segregation,
   sex discrimination, sexism, social barrier, social discrimination,
   socialism, statism, superpatriotism, terrorism, thought control,
   tyranny, ultranationalism, white power, white supremacy,
   xenophobia