microcephalic (adj.)

"small-headed, having an unusually small cranium," either as measured against a certain standard or through disease or faulty development, 1845, from French microcéphalique, from Modern Latin microcephalus, from Greek mikros "small" (see micro-) + kephalē "head" (see cephalo-). Related: Microcephalism; microcephalous (1840); microcephaly (n.).