Flatus

n. accumulation of gas in the stomach or bowels that is expelled through the anus; puff of wind

Flatulence is the presence of a mixture of gases known as flatus in the digestive tract of mammals expelled from the rectum. It is more commonly known as 'farting', 'passing gas', or 'breaking wind' (UK).'
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Flatus /fla·tus/ [L.] 1. gas or air in the gastrointestinal tract. 2. gas or air expelled through the anus. fla·tus n. [more]Flatus - Community and Resources

Noun
1. a reflex that expels intestinal gas through the anus
(synonym) fart, farting, wind, breaking wind
(hypernym) reflex, instinctive reflex, innate reflex, inborn reflex, unconditioned reflex, physiological reaction

Gas in the intestinal tract or passed through the anus. The intestinal gases are hydrogen, nitrogen, carbon dioxide, and methane, all of which are odorless. The unpleasant smell of flatus is the result of trace gases such as indole, skatole, and, most commonly, hydrogen sulfide.