n.an abnormally large head; differs from hydrocephalus because there is no increased intracranial pressure and the overgrowth is symmetrical
同义词：macrocephalymegacephaly
英汉双解大词典
megacephaly/ˌmɛɡəˈsɛfəlɪ/(alsomegalocephaly)
1.
N（名词）
the condition of having an unusually large head or cranial capacity. It can be of congenital origin or result from an abnormal overgrowth of the facial bones 巨头症 → compare microcephaly