a sexual experience/position involving four parties usually 2 males and 2 females. One male lays flat on the ground with an erect penis. the two females then proceed to mount on the mouth and penis. the second male then stands over over the first male in between the two female, whom are facing each other, and receives oral stimulation from both females, orally and anally.
Bob: Hey David! I have two female companions wishing to engage in a quadrilateral.