The Collaborative International Dictionary of English v.0.48:

Nation \Na"tion\, n. [F. nation, L. natio nation, race, orig., a
   being born, fr. natus, p. p. of nasci, to be born, for
   gnatus, gnasci, from the same root as E. kin. [root]44. See
   Kin kindred, and cf. Cognate, Natal, Native.]
   1. (Ethnol.) A part, or division, of the people of the earth,
      distinguished from the rest by common descent, language,
      or institutions; a race; a stock.
      [1913 Webster]

            All nations, and kindreds, and people, and tongues.
                                                  --Rev. vii. 9.
      [1913 Webster]

   2. The body of inhabitants of a country, united under an
      independent government of their own.
      [1913 Webster]

            A nation is the unity of a people.    --Coleridge.
      [1913 Webster]

            Praise the power that hath made and preserved us a
            nation.                               --F. S. Key.
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   3. Family; lineage. [Obs.] --Chaucer.
      [1913 Webster]

   4.
      (a) One of the divisions of university students in a
          classification according to nativity, formerly common
          in Europe.
      (b) (Scotch Universities) One of the four divisions (named
          from the parts of Scotland) in which students were
          classified according to their nativity.
          [1913 Webster]

   5. A great number; a great deal; -- by way of emphasis; as, a
      nation of herbs. --Sterne.
      [1913 Webster]

   Five nations. See under Five.

   Law of nations. See International law, under
      International, and Law.
      [1913 Webster]

   Syn: people; race. See People.
        [1913 Webster]

WordNet (r) 3.0 (2006):

nation
    n 1: a politically organized body of people under a single
         government; "the state has elected a new president";
         "African nations"; "students who had come to the nation's
         capitol"; "the country's largest manufacturer"; "an
         industrialized land" [syn: state, nation, country,
         land, commonwealth, res publica, body politic]
    2: the people who live in a nation or country; "a statement that
       sums up the nation's mood"; "the news was announced to the
       nation"; "the whole country worshipped him" [syn: nation,
       land, country]
    3: United States prohibitionist who raided saloons and destroyed
       bottles of liquor with a hatchet (1846-1911) [syn: Nation,
       Carry Nation, Carry Amelia Moore Nation]
    4: a federation of tribes (especially Native American tribes);
       "the Shawnee nation"

Moby Thesaurus II by Grady Ward, 1.0:

118 Moby Thesaurus words for "nation":
   Everyman, John Doe, Public, ally, animal kingdom, archduchy,
   archdukedom, blood, body politic, breed, brood, buffer state,
   captive nation, chieftaincy, chieftainry, citizenry, city-state,
   clan, class, colony, common man, commonweal, commonwealth,
   community, community at large, constituency, country, county,
   cultural community, culture, deme, domain, dominion, duchy,
   dukedom, dwellers, earldom, empery, empire, estate, ethnic group,
   everybody, everyman, everyone, everywoman, family, folk, folks,
   free city, general public, gens, gentry, grand duchy, habitancy,
   house, inhabitants, kind, kingdom, land, line, lineage,
   linguistic community, mandant, mandate, mandated territory,
   mandatee, mandatory, matriclan, men, nationality, order, patriclan,
   people, people at large, people in general, persons, phratry,
   phyle, plant kingdom, polis, polity, populace, population,
   possession, power, principality, principate, protectorate,
   province, public, puppet government, puppet regime, race, realm,
   republic, satellite, seneschalty, sept, settlement, society,
   sovereign nation, species, speech community, state, stem, stirps,
   stock, strain, sultanate, superpower, territory, toparchia,
   toparchy, totem, tribe, whole people, world, you and me