A very loose uncontrolled movement of the bowels whilst within the time period whose limits are defined by:
a) Handing your boarding pass to the gate agent
and;
b) Taking your seat on a commercial airliner.
"Well, I was just getting on Onur Airflight 711 to Dalaman when I suddenly had a huge spout of boarding diarrhea!"
A more serious version of the Party Pooper. This individual shows the same behaviors. The difference is that just when you think this individual is done with their behavior, they come back and screw up your party even more.