Definition of acephali:
(n) :
(ecclesiastical history) Bishops and certain clergymen not under regular diocesan control.
(n) :
(ecclesiastical history) The Eutychians, a Christian sect in the year 482 without a leader. See http://www.newadvent.org/cathen/01100c.htm.
(n) :
A people reported by Herodotus and Josephus to have no heads or removable heads.
(n) :
A class of levelers in the time of King Henry I.