In particular, the term refers to a strict monophysite sect that separated itself, in the end of the 5th century, from the rule of Peter Mongus, Patriarch of Alexandria, and remained "without king or bishop" until 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.