A man and a woman are in the doggy style position, and another girl is then behind the man and figering his ass. While this is going on, they all simotaniously start peeing and pooing to the mark of a previously agreed apown word, which someone says. usually the word is 'Felix,' but it can be anything really. Also, usually the person who is picked to say the word to commence the pooing and peeing, they usually say it at a comprimising time, when at least one person will be pooed on or peed on. After the shitting, they continue on have sex.
"i head a dirty felix last night with these two chicks, but boy did i get it in the face!"