homoousian

adj

1. (not-comparable)Having the same essence or substance, especially with reference to the first and second persons of the Trinity (Father and Son).

   “But the more fashionable saints of the Arian times, the intrepid Athanasius, the learned Gregory Nazianzen, and the other pillars of the church, who supported with ability and success the Nicene doctrine, appeared to consider the expression of substance as if it had been synonymous with that of nature; and they ventured to illustrate their meaning, by affirming that three men, as they belong to the same common species, are consubstantial, or homoousian to each other.”

noun

1. (historical)One of those, in the 4th century, who accepted the Nicene Creed and maintained that the Son had the same essence or substance with the Father.

   “The Greek word, which was chosen to express this mysterious resemblance, bears so close an affinity to the orthodox symbol, that the profane of every age have derided the furious contests which the difference of a single diphthong excited between the Homoousians and the Homoiousians.”