Brownair is the kind of rectal expulsion that often causes symptoms similar to those experienced by mustard gas victims. An acrid, thick, almost tangible odour.
"Goodness me, Ponsonby just snuck out as I walked in only to be assailed by a cloud of the foulest brownair!"
"Yes, he's a bastard is Ponsonby. Notorious for his obnoxious air biscuits"
A bastardization of the word lunchin, which then formed the term lunchbox to describe an individual who is lunchin hard. It was then evolved into the "brown bag" (as one may use as a vessel for lunch). If you are brown-baggin it, you are trippin out, acting stupid, wayy too high for your own good, idiotically smashed; a drunken fool.