The Collaborative International Dictionary of English v.0.48:

Polity \Pol"i*ty\, n.; pl. Polities. [L. politia, Gr. ?: cf.
   F. politie. See 1st Policy, Police.]
   1. The form or constitution of the civil government of a
      nation or state; the framework or organization by which
      the various departments of government are combined into a
      systematic whole. --Blackstone. Hooker.
      [1913 Webster]

   2. Hence: The form or constitution by which any institution
      is organized; the recognized principles which lie at the
      foundation of any human institution.
      [1913 Webster]

            Nor is possible that any form of polity, much less
            polity ecclesiastical, should be good, unless God
            himself be author of it.              --Hooker.
      [1913 Webster]

   3. Policy; art; management. [Obs.] --B. Jonson.
      [1913 Webster]

   Syn: Policy.

   Usage: Polity, Policy. These two words were originally
          the same. Polity is now confined to the structure of a
          government; as, civil or ecclesiastical polity; while
          policy is applied to the scheme of management of
          public affairs with reference to some aim or result;
          as, foreign or domestic policy. Policy has the further
          sense of skillful or cunning management.
          [1913 Webster]

WordNet (r) 3.0 (2006):

polity
    n 1: the form of government of a social organization [syn:
         civil order, polity]
    2: a politically organized unit
    3: shrewd or crafty management of public affairs; "we was
       innocent of stratagems and polity"

Moby Thesaurus II by Grady Ward, 1.0:

177 Moby Thesaurus words for "polity":
   Everyman, John Doe, Machtpolitik, Public, Realpolitik,
   Tammany Hall, administration, ally, archduchy, archdukedom,
   autarky, bimetallism, body politic, bossism, buffer state,
   captive nation, career politics, chieftaincy, chieftainry,
   circumspection, circumspectness, citizenry, city-state,
   civil government, colony, common man, commonweal, commonwealth,
   community, community at large, confrontation politics,
   consensus politics, consideration, cool judgment, country, county,
   course, creed, direction, discipline, discreetness, discretion,
   discrimination, dispensation, disposition, domain, dominion, duchy,
   dukedom, earldom, economic self-sufficiency, economics in action,
   empery, empire, empirical politics, estate, everybody, everyman,
   everyone, everywoman, folk, folks, form of government, free city,
   free enterprise, free trade, general public, gentry, good judgment,
   governance, government, governmentalism, grand duchy,
   guiding principles, judgment, judiciousness, kid-glove politics,
   kingdom, laissez-faire, laissez-faireism, land, line, localism,
   machine politics, managed currency, management, mandant, mandate,
   mandated territory, mandatee, mandatory, men, nation, nationality,
   noninterference, nonintervention, nullification, oversight,
   partisan politics, partisanism, party line, party principle,
   peanut politics, people, people in general, persons,
   petty politics, plan of action, planned economy, platform, policy,
   polis, political organization, politics, populace, population,
   pork-barrel politics, position, position paper, possession, power,
   power politics, practical politics, pressure-group politics,
   price supports, principality, principate, principles, procedure,
   program, protection, protectionism, protectorate, providence,
   province, prudence, prudentialism, public, public policy,
   pump-priming, puppet government, puppet regime, realm, reflection,
   reflectiveness, reform politics, regime, regimen, regnancy,
   regulation, reign, republic, rule, satellite, sectionalism,
   seneschalty, settlement, silk-stocking politics, society,
   sound judgment, soundness of judgment, sovereign nation,
   sovereignty, state, sultanate, superpower, supervision, sway,
   system of government, territory, thoughtfulness, toparchia,
   toparchy, ward politics, weighing, world, you and me