Source : Webster's Revised Unabridged Dictionary (1913)

Bay window \Bay" win"dow\ (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}.

Source : WordNet®

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