eustathian

from The Century Dictionary.

• Of or pertaining to Eustathius. See II.
• noun A member of the orthodox faction in Antioch in the fourth century a. d., who objected to the replacing of Eustathius, Bishop of Antioch, by an Arian.
• noun A member of an extreme ascetic sect, of the fourth century a. d., probably so called from Eustathius, Bishop of Sebaste in Pontus.