The Collaborative International Dictionary of English v.0.48:

Coup'e \Cou`p['e]"\ (k[=oo]`p[asl]"), n. [F., fr. coup['e], p.
   p. of couper to cut. See Coppice.]
   1. The front compartment of a French diligence; also, the
      front compartment (usually for three persons) of a car or
      carriage on British railways.
      [1913 Webster]

   2. A four-wheeled enclosed carriage for two persons inside,
      with an outside seat for the driver; -- so called because
      giving the appearance of a larger carriage cut off.
      [1913 Webster]

   3. a two-door automobile with front seats and a luggage
      compartment.
      [WordNet 1.5]

WordNet (r) 3.0 (2006):

coupe
    n 1: a car with two doors and front seats and a luggage
         compartment