Ho·moi·ou·si·an 
(hō′moi-sē-ən, -zē-)
(hō′moi-sē-ən, -zē-)n.
An adherent of the Christian doctrine, formulated in the fourth century AD, that Jesus the Son and God the Father are of similar but not of the same substance.
[From Greek homoiousios, of similar substance : homoio-, homeo- + ousiā, substance (from ousa, feminine present participle of einai, to be; see es- in the Appendix of Indo-European roots).]