When one passes gas/farts/toots/etc so severely that it seems to change the density and consistency of the air.
"Man, that fart was so nasty it created some rectal smog! There's even a haze!"
"These beans are going to help me release some rectal smog..."
"These beans are going to help me release some rectal smog..."
by James the Crippler April 23, 2008