‖ exencephalus|ɛksɛnˈsɛfələs| Pl. exencephali. [mod.L. exencephalus, f.Gr. ἐξ out + ἐγκέϕαλος brain.] ‘I. G. St. Hilaire's term for a monstrosity in which the brain lies wholly or chiefly outside the cranial cavity at the back of a very flattened head’ (Syd. Soc.Lex. 1884).