1. Slippage of the lower fragment of a broken long bone upward and beside the proximal portion. 2. Obsolete term denoting a fetal head that is palpable above the symphysis because of cephalopelvic disproportion. 3. Slippage of the bones of the fetal skull that occurs typically after an intrauterine fetal death or prolonged labor marked by cephalopelvic disproportion and extensive molding of the fetal head.