Irrumatio

Irrumation is the act of thrusting of the penis between the legs, breasts, feet, upper thighs (also known as interfemoral sex), mouth and throat, or between the abdomens of two partners. In the ancient Roman sexual vocabulary, irrumatio is strictly a form of os impurum, oral sex, in which a man forces his penis into someone else's mouth, almost always that of another man.