The air that is expelled from an anus before, during or after excretion. Or entirley on its own. The 'dirty air' is usually warm to hot in temperature(about 60-70degreesC), and can be seen on cold days as a vapour cloud that is brownish in colour. Speeds recorded of dirty air have exceeded over 600 mph, over the speed of sound!
That was some foul dirty air i just smelt, johnnys ass stinks!
by Alex Sabga March 03, 2005