Poo Leg refers to the mysterious, involuntary spasm of one's leg as one takes a shit. It may be caused by the inclination to arch one's foot so that the heel levitates above the ground. The intensity of the Poo Leg may depend upon the amount, length, or velocity of the shit in question. Furthermore, it is possible to experience a double Poo Leg which resembles playing a double-bass drum during the into of Van Halen's "Hot For Teacher". Lastly, it is generally accompanied by beer shits following the previous nights transgressions.
Dude 1: Man, that was a sick party last night.
Dude 2: Fuck yeah, I drank my face off last night. I'm talking
Dude 1: All that beer man. How was this morning?
Dude 2: Poo Leg. What else is new.