bay window

noun3

1. •
   A window space projecting outward from the main walls of a building and forming a bay in a room.
2. •
   (slang, figurative) A protruding belly.

   • Marriages that are based only on sex appeal generally fizzle out as soon as he gets a bay window and her figure becomes a bit lumpish. — 1948
3. •
   (slang, figurative) The stomach of a pregnant woman.