The Collaborative International Dictionary of English v.0.48:

County \Coun"ty\ (koun"t[y^]), n.; pl. Counties (-t[i^]z). [F.
   comt['e], fr. LL. comitatus. See Count.]
   1. An earldom; the domain of a count or earl. [Obs.]
      [1913 Webster]

   2. A circuit or particular portion of a state or kingdom,
      separated from the rest of the territory, for certain
      purposes in the administration of justice and public
      affairs; -- called also a shire. See Shire.
      [1913 Webster]

            Every county, every town, every family, was in
            agitation.                            --Macaulay.
      [1913 Webster]

   3. A count; an earl or lord. [Obs.] --Shak.
      [1913 Webster]

   County commissioners. See Commissioner.

   County corporate, a city or town having the privilege to be
      a county by itself, and to be governed by its own sheriffs
      and other magistrates, irrespective of the officers of the
      county in which it is situated; as London, York, Bristol,
      etc. [Eng.] --Mozley & W.

   County court, a court whose jurisdiction is limited to
      county.

   County palatine, a county distinguished by particular
      privileges; -- so called a palatio (from the palace),
      because the owner had originally royal powers, or the same
      powers, in the administration of justice, as the king had
      in his palace; but these powers are now abridged. The
      counties palatine, in England, are Lancaster, Chester, and
      Durham.

   County rates, rates levied upon the county, and collected
      by the boards of guardians, for the purpose of defraying
      the expenses to which counties are liable, such as
      repairing bridges, jails, etc. [Eng.]

   County seat, a county town. [U.S.]

   County sessions, the general quarter sessions of the peace
      for each county, held four times a year. [Eng.]

   County town, the town of a county, where the county
      business is transacted; a shire town.
      [1913 Webster]

WordNet (r) 3.0 (2006):

county
    n 1: (United Kingdom) a region created by territorial division
         for the purpose of local government; "the county has a
         population of 12,345 people"
    2: (United States) the largest administrative district within a
       state; "the county plans to build a new road"

Moby Thesaurus II by Grady Ward, 1.0:

93 Moby Thesaurus words for "county":
   Kreis, ally, archbishopric, archdiocese, archduchy, archdukedom,
   arrondissement, bailiwick, bishopric, body politic, borough,
   buffer state, canton, captive nation, chieftaincy, chieftainry,
   city, city-state, colony, commonweal, commonwealth, commune,
   congressional district, constablewick, country, departement,
   diocese, district, domain, dominion, duchy, dukedom, earldom,
   electoral district, electorate, empery, empire, free city,
   government, grand duchy, hamlet, hundred, kingdom, land,
   magistracy, mandant, mandate, mandated territory, mandatee,
   mandatory, metropolis, metropolitan area, nation, nationality,
   oblast, okrug, parish, polis, polity, possession, power, precinct,
   principality, principate, protectorate, province,
   puppet government, puppet regime, realm, region, republic, riding,
   satellite, seneschalty, settlement, sheriffalty, sheriffwick,
   shire, shrievalty, soke, sovereign nation, stake, state, sultanate,
   superpower, territory, toparchia, toparchy, town, township,
   village, wapentake, ward



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

COUNTY. A district into which a state is divided.
     2. The United States are generally divided into counties; counties are
divided into townships or towns.
     3. In Pennsylvania the division of the province into three Counties,
viz. Philadelphia, Bucks and Chester, was one of the earliest acts of
William Penn, the original proprietary. There is no printed record of this
division, or of the original boundaries of these counties. Proud says it was
made about the year 1682. Proud's Hist. vol. 1 p. 234 vol. 2, p. 258.
     4. In some states, as Illinois; 1 Breese, R. 115; a county is
considered as a corporation, in others it is only a quasi corporation. 16
Mass. R. 87; 2 Mass. R. 644 7 Mass. R. 461; 1 Greenl. R. 125; 3 Greenl. R.
131; 9 Greenl. R. 88; 8 John. R. 385; 3 Munf. R. 102. Frequent difficulties
arise on the division of a county. On this subject, see 16 Mass. R. 86 6 J.
J. Marsh. 147; 4 Halst. R. 357; 5 Watts, R. 87 1 Cowen, R. 550; 6 Cowen, R.
642; Cowen, R. 640; 4 Yeates, R. 399 10 Mass. Rep. 290; 11 Mass. Rep. 339.
     5. In the English law this word signifies the same as shire, county
being derived from the French and shire from the Saxon. Both these words
signify a circuit or portion of the realm, into which the whole land is
divided, for the better government thereof, and the more easy administration
of justice. There is no part of England that is not within some county, and
the shire-reve, (sheriff) originally a yearly officer, was the governor of
the county. Four of the counties of England, viz. Lancaster, Chester, Durham
and Ely, were called counties Palatine, which were jurisdictions of a
peculiar nature, and held by, especial charter from the king. See stat. 27
H. VIII. c. 25.