anencephaly (n.), anencephalic (adj.)

synonym: anencephalia
https://doi.org/10.1351/goldbook.10390

Congenital absence of a major portion of the brain and its meninges, skull, and scalp that results from abnormal embryonic development.

Source:
PAC, 2016, 88, 713. (Glossary of terms used in developmental and reproductive toxicology (IUPAC Recommendations 2016)) on page 722 [Terms] [Paper]