borborygmus

borborygmus \bawr-buh-RIG-muhs\, noun:

a rumbling or gurgling sound caused by the movement of gas in the intestines.

"The stertorous borborygmus of the dyspeptic Carlyle!" declaimed Willie Weaver, and beamed through his spectacles. The mot, he flattered himself, could hardly have been more exquisitely juste.
-- Aldous Huxley, Point Counter Point, 1928

Then her stomach grumbled and spoiled the silence. Quickly, Patsy pressed her hand against her complaining belly, and hoped that Ray had not heard it. "Suffering from borborygmus, I hear," Ray dead-panned dryly.
-- Bonnie Gardner, Sergeant Darling, 2005

Borborygmus comes from the Greek word borborygmós which meant "intestinal rumbling."