Borborygmus (plural borborygmi) (from Greek βορβορυγμος) is the rumbling sound produced by the movement of gas through the intestines of animals. The word borborygmus is an actual onomatopoeia for this rumbling.

The "rumble" or "growl" sometimes heard from the stomach is a normal part of digestion. It originates in the stomach or upper part of the small intestine as muscles contract to move food and digestive juices down the gastrointestinal tract.

Although this muscle contraction happens whether or not food is present, rumbles are more common after the animal has gone several hours without eating. This may be why a "growling" stomach is often associated with hunger.

Rumbles may also occur when there is incomplete digestion of food that can lead to excess gas in the intestine. In humans this can be due to incomplete digestion of carbohydrate-containing foods including milk and other dairy products (lactose intolerance or the use of α-glucosidase inhibitors by diabetics), gluten (protein in wheat, barley, and rye) (celiac disease), fruits, vegetables, beans, legumes, and high-fiber whole grains. In rare instances excessive abdominal noise may be a sign of digestive disease, especially when accompanied by abdominal bloating, abdominal pain, diarrhea or constipation.