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]

WordNet (r) 3.0 (2006):

bay window
    n 1: slang for a paunch [syn: pot, potbelly, bay window,
         corporation, tummy]
    2: a window that sticks out from the outside wall of a house
       [syn: bay window, bow window]