ACA'CIANS, in Church History, were certain sects, so denominated from their leaders, Acacius, bishop of Cesarea, and Acacius, patriarch of Constantinople. Some of these maintained that the Son was only a similar, not the same, substance with the Father; others, that he was not only a distinct but a dissimilar substance.
Source: Webster's 1828 American Dictionary ↗ · public-domain · returned verbatim, no AI