Semi-Arian \Sem`i-A"ri*an\, n. [See {Arian}.] (Eccl. Hist.) A member of a branch of the Arians which did not acknowledge the Son to be consubstantial with the Father, that is, of the same substance, but admitted him to be of a like substance with the Father, not by nature, but by a peculiar privilege. Semi-Arian \Sem"i-A"ri*an\, a. Of or pertaining to Semi-Arianism.