A Poot Whoo is someone who is famous for letting out tremendous amounts of gas in the form of flatuations. Generally these powerful burst bring tears to the eye and smell as if someone has stained the air.
John: Dude, did you invite Rocky to the steam room party?
Ted: No man. Rocky is a poot whoo. Remember that time we were stuck in that elevator? The repairmen had to completly sanitize the 4th and 5th floors.
John: Oh yeah! Good call.