The Collaborative International Dictionary of English v.0.48:

Sleeping \Sleep"ing\,
   a. & n. from Sleep.
   [1913 Webster]

   Sleeping car, a railway car or carrriage, arranged with
      apartments and berths for sleeping.

   Sleeping partner (Com.), a dormant partner. See under
      Dormant.

   Sleeping table (Mining), a stationary inclined platform on
      which pulverized ore is washed; a kind of buddle.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Car \Car\, n. [OF. car, char, F. cahr, fr. L. carrus, Wagon: a
   Celtic word; cf. W. car, Armor. karr, Ir. & Gael. carr. cf.
   Chariot.]
   1. A small vehicle moved on wheels; usually, one having but
      two wheels and drawn by one horse; a cart.
      [1913 Webster]

   2. A vehicle adapted to the rails of a railroad. [U. S.]
      [1913 Webster]

   Note: In England a railroad passenger car is called a railway
         carriage; a freight car a goods wagon; a platform car a
         goods truck; a baggage car a van. But styles of car
         introduced into England from America are called cars;
         as, tram car. Pullman car. See Train.
         [1913 Webster]

   3. A chariot of war or of triumph; a vehicle of splendor,
      dignity, or solemnity. [Poetic].
      [1913 Webster]

            The gilded car of day.                --Milton.
      [1913 Webster]

            The towering car, the sable steeds.   --Tennyson.
      [1913 Webster]

   4. (Astron.) The stars also called Charles's Wain, the Great
      Bear, or the Dipper.
      [1913 Webster]

            The Pleiads, Hyads, and the Northern Car. --Dryden.
      [1913 Webster]

   5. The cage of a lift or elevator.
      [1913 Webster]

   6. The basket, box, or cage suspended from a balloon to
      contain passengers, ballast, etc.
      [1913 Webster]

   7. A floating perforated box for living fish. [U. S.]
      [1913 Webster]

   Car coupling, or Car coupler, a shackle or other device
      for connecting the cars in a railway train. [U. S.]

   Dummy car (Railroad), a car containing its own steam power
      or locomotive.

   Freight car (Railrood), a car for the transportation of
      merchandise or other goods. [U. S.]

   Hand car (Railroad), a small car propelled by hand, used by
      railroad laborers, etc. [U. S.]

   Horse car, or Street car, an omnibus car, draw by horses
      or other power upon rails laid in the streets. [U. S.]

   Palace car, Drawing-room car, Sleeping car, Parlor
   car, etc. (Railroad), cars especially designed and furnished
      for the comfort of travelers.
      [1913 Webster]

WordNet (r) 3.0 (2006):

sleeping car
    n 1: a passenger car that has berths for sleeping [syn:
         sleeping car, sleeper, wagon-lit]