A place where wild orgies are held. It stems from Roman roots, because they had random group sex all the time. All the fucking time. Because of this, some dumbshit Roman said hey lets make a building to have orgies in! It then became the Roman standard for emperors to try to construct the grandest Orgitoriums to hold the most hot italian bitches. They constantly competed with each other, thus filling rome with many such Orgitoriums. Many of these still survive today, but be careful where you step ;)
Sextus: Hey Octavius lets go to the Orgitorium to celebrate!
Octavius: Rofl YAY!