What is the term for an infant born without a brain?

The term for an infant born without a brain is anencephalic, which refers specifically to a severe neural tube defect that results in the partial or complete absence of the brain and skull. Infants with this condition typically have a rudimentary brain stem but lack the major parts of the brain, such as the cerebrum and cerebellum. This serious condition can affect the function and viability of the infant, and it is often diagnosed during prenatal imaging.

The other terms, while they relate to medical and developmental conditions, do not specifically describe the absence of the brain. "Congenital disorder" is a broad term that encompasses any condition that is present at birth, but it is not specific to brain development issues. "Neural deficit" refers to any impairment in the nervous system functions but does not imply complete absence of brain tissue. "Brain malformation" involves abnormalities in the structure of the brain but does not necessarily indicate a lack of brain tissue entirely. Anencephaly is thus the precise term that directly correlates to the condition described in the question.