cranioschisis noun1 •A developmental birth defect in which the cranium fails to close completely, so that the brain is exposed to the amnios and eventually degenerates, causing anencephaly.E. M. Butt et al. have reported the production of meningoceles and cranioschises in chick embryos with 0.5 to 1.0 mg. of lead nitrate (21). — 1953 formscranioschises
