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.
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   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.
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   3. Any portion of territory of undefined extent; a region; a
      country; a tract.
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            These districts which between the tropics lie.
                                                  --Blackstone.
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   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