QUINQUENNIUM Meaning of QUINQUENNIUM in English [ kwɪŋ'kwɛnɪəm ]■ noun ( plural quinquennia -nɪə or ~s ) a period of five years.OriginC17: from L., from quinque 'five' + annus 'year'. Concise Oxford English vocab. Сжатый оксфордский словарь английского языка. 2004