The Collaborative International Dictionary of English v.0.48:

Bay window \Bay" win"dow\
   1. (Arch.) A window forming a bay or recess in a room, and
      projecting outward from the wall, either in a rectangular,
      polygonal, or semicircular form; -- often corruptly called
      a bow window.

   Syn: bay window, bow window, bow-window.
        [1913 Webster + WordNet 1.5]

   2. a protruding abdomen. [informal]

   Syn: belly, paunch, pot, potbelly, corporation, tummy.
        [WordNet 1.5]

The Collaborative International Dictionary of English v.0.48:

Bow \Bow\ (b[=o]), n. [OE. bowe, boge, AS. boga, fr. AS.
   b[=u]gan to bend; akin to D. boog, G. bogen, Icel. bogi. See
   Bow, v. t.]
   [1913 Webster]
   1. Anything bent, or in the form of a curve, as the rainbow.
      [1913 Webster]

            I do set my bow in the cloud.         --Gen. ix. 13.
      [1913 Webster]

   2. A weapon made of a strip of wood, or other elastic
      material, with a cord connecting the two ends, by means of
      which an arrow is propelled.
      [1913 Webster]

   3. An ornamental knot, with projecting loops, formed by
      doubling a ribbon or string.
      [1913 Webster]

   4. The U-shaped piece which embraces the neck of an ox and
      fastens it to the yoke.
      [1913 Webster]

   5. (Mus.) An appliance consisting of an elastic rod, with a
      number of horse hairs stretched from end to end of it,
      used in playing on a stringed instrument.
      [1913 Webster]

   6. An arcograph.
      [1913 Webster]

   7. (Mech. & Manuf.) Any instrument consisting of an elastic
      rod, with ends connected by a string, employed for giving
      reciprocating motion to a drill, or for preparing and
      arranging the hair, fur, etc., used by hatters.
      [1913 Webster]

   8. (Naut.) A rude sort of quadrant formerly used for taking
      the sun's altitude at sea.
      [1913 Webster]

   9. (Saddlery) sing. or pl. Two pieces of wood which form the
      arched forward part of a saddletree.
      [1913 Webster]

   Bow bearer (O. Eng. Law), an under officer of the forest
      who looked after trespassers.

   Bow drill, a drill worked by a bow and string.

   Bow instrument (Mus.), any stringed instrument from which
      the tones are produced by the bow.

   Bow window (Arch.) See Bay window.

   To draw a long bow, to lie; to exaggerate. [Colloq.]
      [1913 Webster]

WordNet (r) 3.0 (2006):

bow window
    n 1: a window that sticks out from the outside wall of a house
         [syn: bay window, bow window]