The act of taking your dick out of a chick's vagina and finding that she shed her nasty pubes on you, and there are crabs running around that look like little cats.
You immediately lose your stiffy, and it slumps there in semi-boner mode-- thus looking like a cat's leg hanging from your southern region.
John: Bro, it was a nice f*ck, but I got a nasty little foreign surprise.
Mitchell: What was it?
John: I ended with an Egyptian Cat-Leg, and had to walk home with that deflated animal hanging from my groin.
Mitchell: That's f*ckin gross. Get away from me.