homoousian
noun
ho·mo·ou·si·an hō-ˌmō-ˈü-zē-ən 
hä-,
-ˈü-sē-
: an adherent of an ecclesiastical party of the fourth century holding to the doctrine of the Nicene Creed that the Son is of the same substance with the Father
Word History
Etymology
Late Greek homoousios of the same substance, from Greek hom- + ousia substance — more at homoiousian
First Known Use
1565, in the meaning defined above