The Collaborative International Dictionary of English v.0.48:

Republican \Re*pub"lic*an\ (r?-p?b"l?-kan), n.
   1. One who favors or prefers a republican form of government.
      [1913 Webster]

   2. (U.S.Politics) A member of the Republican party.
      [1913 Webster]

   3. (Zool.)
      (a) The American cliff swallow. The cliff swallows build
          their nests side by side, many together.
      (b) A South African weaver bird (Philetaerus socius).
          These weaver birds build many nests together, under a
          large rooflike shelter, which they make of straw.
          [1913 Webster]

   Red republican. See under Red.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Republican \Re*pub"lic*an\ (-l?-kan), a. [F. r['e]publicain.]
   1. Of or pertaining to a republic.
      [1913 Webster]

            The Roman emperors were republican magistrates named
            by the senate.                        --Macaulay.
      [1913 Webster]

   2. Consonant with the principles of a republic; as,
      republican sentiments or opinions; republican manners.
      [1913 Webster]

   Republican party. (U.S. Politics)
      (a) An earlier name of the Democratic party when it was
          opposed to the Federal party. Thomas Jefferson was its
          great leader.
      (b) One of the existing great parties. It was organized in
          1856 by a combination of voters from other parties for
          the purpose of opposing the extension of slavery, and
          in 1860 it elected Abraham Lincoln president.
          [1913 Webster]

WordNet (r) 3.0 (2006):

republican
    adj 1: relating to or belonging to the Republican Party; "a
           Republican senator"; "Republican party politics"
    2: having the supreme power lying in the body of citizens
       entitled to vote for officers and representatives responsible
       to them or characteristic of such government; "the United
       States shall guarantee to every state in this union a
       republican form of government"- United States Constitution;
       "a very republican notion"; "so little republican and so much
       aristocratic sentiment"- Philip Marsh; "our republican and
       artistic simplicity"-Nathaniel Hawthorne
    n 1: a member of the Republican Party
    2: an advocate of a republic (usually in opposition to a
       monarchy)
    3: a tributary of the Kansas River that flows from eastern
       Colorado eastward through Nebraska and Kansas [syn:
       Republican, Republican River]

Moby Thesaurus II by Grady Ward, 1.0:

37 Moby Thesaurus words for "republican":
   absolute, aristocratic, authoritarian, autocratic, autonomous,
   bureaucratic, civic, civil, constitutional, democratic, despotic,
   dictatorial, fascist, federal, federalist, federalistic,
   governmental, gubernatorial, heteronomous, matriarchal,
   matriarchic, monarchal, monarchial, monarchic, monocratic,
   official, oligarchal, oligarchic, parliamentarian, parliamentary,
   patriarchal, patriarchic, pluralistic, political, self-governing,
   theocratic, totalitarian



Moby Thesaurus II by Grady Ward, 1.0:

19 Moby Thesaurus words for "Republican":
   Conservative, Democrat, Labourite, Tory, Whig, heeler, loyalist,
   partisan, party faithful, party hack, party man, party member,
   party wheelhorse, registered Democrat, registered Republican,
   regular, stalwart, ward heeler, wheelhorse