acephalan
/(ˌ)eɪˈsɛfələn/ /(ˌ)eɪˈsɛf(ə)lən/ /(ˌ)eɪˈkɛfələn/Zoology. Now rare
adjective
Of the former invertebrate class Acephala; designating or relating to this class.
Origin
Mid 19th century (in an earlier sense). From Acephala + -an. With the use as adjective compare earlier acephalous.