athero-. Definitions: 1. Gruellike, soft, pasty materials; atheroma, atheromatous. The definition information for athero-is provided by Stedman's. You can search our medical dictionary here.Stedman's, part of Lippincott Williams & Wilkins, provides a comprehensive line of health-science publications for healthcare professionals and medical students.he definition information for athero-is provided by Stedman's. You can search our medical dictionary here.