What does flatus mean?
Flatus is the formal term for gas produced in the stomach or intestines, particularly when it is expelled through the anus. Derived from the Latin verb flare, meaning 'to blow', it entered English in the early seventeenth century as part of the vocabulary of learned medicine, and it retains that professional tone today: you will meet it in hospital notes, surgical textbooks, and dietary advice rather than in casual chat, where people simply say 'gas' or 'wind'. Clinically, the passing of flatus is a meaningful sign — surgeons, for example, look for it as evidence that normal bowel function has resumed after an operation. A rarer, older sense treats flatus as any puff or blast of air, even a divine inspiration, though this usage has largely fallen away. Related derivatives include flatulent and flatulence, which describe the condition rather than the substance. Precise, dignified, and faintly comic all at once, flatus shows how scientific Latin lends gravity to even the most everyday bodily phenomena.
nounGas generated in the stomach or intestines, especially that which is expelled through the anus; more broadly, in older usage, any puff or blast of air or breath.
- Gas formed in the stomach or intestines and expelled through the anus.
- A puff or blowing of air; a breath or blast of wind (chiefly in older literary and medical usage).
"The patient reported bloating and excessive flatus after meals."
"After the surgery, the nurses were waiting to see whether he could pass flatus, a sign his digestion was recovering."
"Ancient physicians blamed colic on an accumulation of flatus in the bowels."
The plural exists but is rarely used; in practice flatus is treated as an uncountable mass noun in both medical and general contexts.
"Different foods produce flatuses of varying volume and odor."
It sounds like a spell from Harry Potter, but flatus is a respectable Latin-derived term that physicians have used for gas since ancient Rome.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of flatus
Flatus comes directly from Latin, where it is the past participle of flare, 'to blow', and so literally means 'a blowing'. It was borrowed into English in the early seventeenth century, chiefly through medical writing, alongside sibling terms built on the same root such as inflate, deflate, and conflate. Its derivative flatulent and the compound flatulence preserve the same breath-blowing idea applied to the digestive tract.
Related word forms
How flatus is actually used
Formal and largely clinical in register; ordinary conversation favors words like 'gas' or 'wind'. The broader sense ('a puff of air') is now rare and mostly historical. Plural form 'flatuses' exists but is uncommon; the word usually functions as an uncountable mass noun.
Easily confused with flatus
Flatus refers to the gas itself, while flatulence refers to the condition of having or releasing such gas.