Also known as the abdominal muscles; the muscles over the stomach below the ribbs (i.e: rib cage), containing normally 6 firm muscles packed together (i.e: 6 pack). If well toned they can be quite strong and hard, often bigger with men, they develope over purberty normally.
Dude: Hey what's up? (walking accross the beach)
Chick: Wow! Nice abbs hottie, wanna go for a swim?
Dude: (whispers) Thank you abbs...