Source : Webster's Revised Unabridged Dictionary (1913)

Homoousian \Ho`mo*ou"si*an\, a.
   Of or pertaining to the Homoousians, or to the doctrines they
   held.

Homoousian \Ho`mo*ou"si*an\, n. [Gr. ?; ? the same + ? being,
   essence, substance.] (Eccl. Hist.)
   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; -- opposed to homoiousian.