Semi-Arian UK /ˌsɛ.miˈɛəɹi.ən/US /ˌsɛ.miˈɛɹi.ən/adjective 1noun 1forms 1 adjective1 •(historical) Of or relating to the Semi-Arianism movement.The highways of the East were crowded with Homoousian, and Arian, and Semi-Arian, and Eunomian bishops, who struggled to outstrip each other in the holy race: […]. — 1781 noun1 •(historical) A member of the Semi-Arianism movement. formsSemi-Arians