erythroblastosis fetalis: severe anemia in newborn babies; the result of Rh incompatibility between maternal and fetal blood; typically occurs when the child of an Rh-negative mother inherits Rh-positive blood from the father; can be diagnosed before birth by amniocentesis
entity: that which is perceived or known or inferred to have its own distinct existence (living or nonliving)
jackknife: a dive in which the diver bends to touch the ankles before straightening out