The Collaborative International Dictionary of English v.0.48:

Congressional \Con*gres"sion*al\, a.
   Of or pertaining to a congress, especially, to the Congress
   of the United States; as, congressional debates.
   [1913 Webster]

         Congressional and official labor.        --E. Everett.
   [1913 Webster]

   Congressional District, one of the divisions into which a
      State is periodically divided (according to population),
      each of which is entitled to elect a Representative to the
      Congress of the United States.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

District \Dis"trict\, n. [LL. districtus district, fr. L.
   districtus, p. p. of distringere: cf. F. district. See
   Distrain.]
   1. (Feudal Law) The territory within which the lord has the
      power of coercing and punishing.
      [1913 Webster]

   2. A division of territory; a defined portion of a state,
      town, or city, etc., made for administrative, electoral,
      or other purposes; as, a congressional district, judicial
      district, land district, school district, etc.
      [1913 Webster]

            To exercise exclusive legislation . . . over such
            district not exceeding ten miles square. --The
                                                  Constitution
                                                  of the United
                                                  States.
      [1913 Webster]

   3. Any portion of territory of undefined extent; a region; a
      country; a tract.
      [1913 Webster]

            These districts which between the tropics lie.
                                                  --Blackstone.
      [1913 Webster]

   Congressional district. See under Congressional.

   District attorney, the prosecuting officer of a district or
      district court.

   District court, a subordinate municipal, state, or United
      States tribunal, having jurisdiction in certain cases
      within a judicial district.

   District judge, one who presides over a district court.

   District school, a public school for the children within a
      school district. [U.S.]

   Syn: Division; circuit; quarter; province; tract; region;
        country.
        [1913 Webster]

WordNet (r) 3.0 (2006):

congressional district
    n 1: a territorial division of a state; entitled to elect one
         member to the United States House of Representatives

Moby Thesaurus II by Grady Ward, 1.0:

55 Moby Thesaurus words for "congressional district":
   Kreis, archbishopric, archdiocese, arrondissement, bailiwick,
   bishopric, borough, canton, city, close borough, commune,
   constablewick, county, departement, diocese, district, duchy,
   election district, electoral district, electorate, gerrymander,
   gerrymandered district, government, hamlet, hundred, magistracy,
   metropolis, metropolitan area, oblast, okrug, parish,
   pocket borough, precinct, principality, province, region, riding,
   rotten borough, safe district, sheriffalty, sheriffwick, shire,
   shrievalty, silk-stocking district, single-member district, soke,
   stake, state, swing district, territory, town, township, village,
   wapentake, ward