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 (https://doi.org/10.1515/pac-2015-1202)