The Collaborative International Dictionary
Heteroousian
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.
Heteroousian
Heteroousian \Het`er*o*ou`si*an\, a. [Hetero- + Gr. ? being, essence.] Having different essential qualities; of a different nature.
Wiktionary
heteroousian
a. having different essence or substance, especially with reference to the first and second persons of the Trinity