Source : Webster's Revised Unabridged Dictionary (1913)

Federalist \Fed"er*al*ist\, n. [Cf. F. f['e]d['e]raliste.]
   An advocate of confederation; specifically (Amer. Hist.), a
   friend of the Constitution of the United States at its
   formation and adoption; a member of the political party which
   favored the administration of president Washington.

Source : WordNet®

Federalist
     n 1: a member of a former political party in the United States
          that favored a strong centralized federal government
     2: an advocate of federalism