floating head [AS, flotian, to float, heafod] , a condition that exists when the biparietal diameter of the fetal head is above the plane of the pelvic inlet. The term comes from the ease with which the fetal head is pushed upward on pelvic examination (i.e., it “floats away”) as compared to the engaged fetal head, when such movement is difficult if not impossible. See also ballottement, engagement.