SEXENNIUM Meaning of SEXENNIUM in English [ sɛk'sɛnɪəm ]■ noun ( plural sexennia -nɪə or ~s ) rare a period of six years.Origin1950s: L., from sex 'six' + annus 'year'. Concise Oxford English vocab. Сжатый оксфордский словарь английского языка. 2004