The Collaborative International Dictionary of English v.0.48:

Courthouse \Court"house`\ (k[=o]rt"hous`), n.
   1. A house in which established courts are held, or a house
      appropriated to courts and public meetings. [U.S.]
      [1913 Webster]

   2. A county town; -- so called in Virginia and some others of
      the Southern States.
      [1913 Webster]

            Providence, the county town of Fairfax, is unknown
            by that name, and passes as Fairfax Court House.
                                                  --Barlett.
      [1913 Webster]

WordNet (r) 3.0 (2006):

courthouse
    n 1: a government building that houses the offices of a county
         government
    2: a building that houses judicial courts

Moby Thesaurus II by Grady Ward, 1.0:

20 Moby Thesaurus words for "courthouse":
   capitol, city hall, community center, county building,
   county courthouse, court, courtroom, dock, fire station, firehouse,
   jury box, municipal building, police headquarters, police station,
   precinct house, statehouse, town hall, town house, witness box,
   witness stand