vicennial adjective 2noun 3forms 1 adjective2 •Occurring once every twenty years. •Lasting for twenty years. noun3 •A twenty-year periodThe maps are presented at 20-year intervals (vicennials) because of the nature of the data, particularly for years prior to 1960 when estimation procedures were not nearly as developed as today. — 2022 •A twentieth anniversary. •(historical) Synonym of vicennalia, the festival and religious ritual held in the 20th year of a Roman emperor's reign.Roman coins mentioning the vota publica for Macrinus are RIC IV.1 5–13; on vota publica for the decennials and vicennials of emperors in the 2nd and 3rd c. ad, see Chastagnol 1984. — 2022 formsvicennials
