Theol. of or holding the teaching that God the Father and God the Son are of a similar nature, not of the same nature
noun
an adherent of this teaching
See homoiousian in American Heritage Dictionary 4
(hōˌmoi-o͞oˈsē-ən, -zē-)
noun
A member of the Semi-Arian party in the fourth century A.D. that held that Jesus the Son and God the Father were of similar but not of the same substance.