acephalan,a.andn.|əˈsɛfələn|[f.prec.+ -an.]1.adj.Of or pertaining to the acephala.Mod.An animal of the acephalan type..One skilled in acephalan zoology.2.n.An animal of the division acephala.1856WoodwardMan.Mollusca 49Viviparous reproduction..appears to take place in the acephalans.