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