Entry 2 senses · 2 variants Webster, 1913 Acephalan · A·ceph·a·lan · IPA /eɪˈsɛ.fə.lən/ n. a. 01 n. Same as Acephal. 1. Same as Acephal. See: Acephal 02 a. Belonging to the Acephala. 1. Belonging to the Acephala.(Zool.)