Source : Webster's Revised Unabridged Dictionary (1913)

Coessential \Co`es*sen"tial\, a.
   Partaking of the same essence. -- {Co`es*sen"tial*ly}, adv.

         We bless and magnify that coessential Spirit, eternally
         proceeding from both [The Father and the Son].
                                                  --Hooker.