"Acephali" (from a-, "without," and kephale, "head") is a term applied to several sects as having no head or leader; and in particular to a strict monophysite sect that separated itself, in the end of the 5th century, from the rule of Peter Mongus, the patriarch of Alexandria, and remained "without king or bishop" till they were reconciled by Mark II (799 - 819).
The term is also used to denote clerici vagantes, i.e. clergy without title or benefice, picking up a living anyhow. Certain persons in England during the reign of King Henry I of England were called Acephali because they had no lands by virtue of which they could acknowledge a superior lord.
The name is also given to certain legendary races described by ancient naturalists and geographers as having no heads, their mouths and eyes being in their breasts, generally identified with Pliny's Blemmyae.
On a subject which engrossed the thoughts and discourses of men, it was difficult to preserve an exact neutrality; a book, a sermon, a prayer, rekindled the flame of controversy; and the bonds of communion were alternately broken and renewed by the private animosity of the bishops.
The space between Nestorius and Eutyches was filled by a thousand shades of language and opinion; the acephali of Egypt, and the Roman pontiffs, of equal valor, though of unequal strength, may be found at the two extremities of the theological scale.
The acephali, without a king or a bishop, were separated above three hundred years from the patriarchs of Alexandria, who had accepted the communion of Constantinople, without exacting a formal condemnation of the synod of Chalcedon.