A member of a 4th-cent. Christian group who believed that the Son and the Spirit only emerged from the Divine Unity for the purposes of creation and redemption, and will return to it after the redemptive work is achieved.
The personal commitment of Marcellus of Ancyra to this doctrine has been disputed.
Early 17th century; earliest use found in Thomas Rogers (c1553–1616), religious controversialist and Church of England clergyman. From post-classical Latin Marcellianus (400) from the name of Marcellus, bishop of Ancyra (ca.d. 280–374; see note below) + -ianus.