Heteroousian \Het`er*o*ou`si*an\, a. [Hetero- + Gr. ? being, essence.] Having different essential qualities; of a different nature. [1913 Webster]
Heteroousian \Het`er*o*ou"si*an\, n. (Eccl. Hist.) One of those Arians who held that the Son was of a different substance from the Father. [1913 Webster]