The Collaborative International Dictionary of English v.0.48:

Federalism \Fed"er*al*ism\, n. [Cf. F. f['e]d['e]ralisme.]
   The principles of Federalists or of federal union.
   [1913 Webster]

WordNet (r) 3.0 (2006):

federalism
    n 1: the idea of a federal organization of more or less self-
         governing units

Moby Thesaurus II by Grady Ward, 1.0:

22 Moby Thesaurus words for "federalism":
   Nazism, centralism, collectivism, communism, constitutionalism,
   democratism, fascism, feudalism, feudality, governmentalism,
   imperialism, monarchism, national socialism, neofascism,
   parliamentarianism, parliamentarism, pluralism,
   political principles, republicanism, royalism, socialism,
   statism