Orgy

In modern usage, an orgy is a sex party where guests freely engage in open and unrestrained sexual activity or group sex. Swingers' parties do not always conform to this designation, because at many swinger parties the sexual partners may all know each other or at least have some commonality among economic class, educational attainment or other shared attributes. Some swingers contend that an orgy, as opposed to a sex party, requires some anonymity of sexual partners in complete sexual abandon. Other kinds of "sex parties" may fare less well with this labeling. Participation... Wikipedia