The Collaborative International Dictionary of English v.0.48:

Confederation \Con*fed`er*a"tion\, n. [L. confoederatio: cf. F.
   conf['e]d['e]ration.]
   1. The act of confederating; a league; a compact for mutual
      support; alliance, particularly of princes, nations, or
      states.
      [1913 Webster]

            The three princes enter into some strict league and
            confederation among themselves.       --Bacon.
      [1913 Webster]

            This was no less than a political confederation of
            the colonies of New England.          --Palfrey.
      [1913 Webster]

   2. The parties that are confederated, considered as a unit; a
      confederacy.
      [1913 Webster]

   Articles of confederation. See under Article.
      [1913 Webster]

WordNet (r) 3.0 (2006):

confederation
    n 1: the state of being allied or confederated [syn: alliance,
         confederation]
    2: a union of political organizations [syn: confederation,
       confederacy, federation]
    3: the act of forming an alliance or confederation [syn:
       confederation, alliance]

Moby Thesaurus II by Grady Ward, 1.0:

103 Moby Thesaurus words for "confederation":
   Anschluss, Bund, Rochdale cooperative, addition, affiliation,
   agglomeration, aggregation, agreement, alignment, alliance,
   amalgamation, anschluss, assemblage, assimilation, association,
   axis, band, blend, blending, bloc, body, cabal, cahoots, cartel,
   centralization, coadunation, coalescence, coalition, colleagueship,
   college, collegialism, collegiality, combination, combine, combo,
   common market, composition, comradeship, confederacy,
   confraternity, congeries, conglomeration, conjugation, conjunction,
   consolidation, conspiracy, consumer cooperative, cooperative,
   cooperative society, copartnership, copartnery, corps, council,
   credit union, customs union, economic community, ecumenism,
   embodiment, encompassment, enosis, federalization, federation,
   fellowship, fraternalism, fraternity, fraternization,
   free trade area, freemasonry, fusion, gang, group, grouping,
   hookup, inclusion, incorporation, integration, junction, junta,
   league, machine, marriage, meld, melding, merger, mob, package,
   package deal, partnership, political machine, ring, society,
   sodality, solidification, sorority, syncretism, syndication,
   syneresis, synthesis, tie-in, tie-up, unification, union,
   wedding



Bouvier's Law Dictionary, Revised 6th Ed (1856):

CONFEDERATION, government. The name given to that form of government which
the American colonies, on shaking off the British yoke, devised for their
mutual safety and government.
     2. The articles of confederation, (q.v.) were finally adopted on the
15th of November, 1777, and with the exception of Maryland, which, however,
afterwards also agreed to them, were speedily adopted by the United States,
and by which they were formed into a federal @bod y, and went into force on
the first day of March, 1781; 1 Story Const. Sec. 225; and so remained until
the adoption of the present constitution, which acquired the force of the
supreme law of the land on the first Wednesday of March, 1789. 5 Wheat. R.
420. Vide Articles of Confederation.