microcephaly Syllabification: (mi·cro·ceph·a·ly)Pronunciation: /ˌmīkrōˈsefəlē/Definition of microcephaly noun Medicine abnormal smallness of the head, a congenital condition associated with incomplete brain development. Derivatives microcephalicPronunciation: /-səˈfalik/ adjective & noun microcephalousPronunciation: /-ˈsefələs/ adjective microcephaly in other Oxford dictionaries Definition of microcephaly in the British & World English dictionary