NONAGENARIAN Meaning of NONAGENARIAN in English [ ˌnɒnədʒɪ'nɛ:rɪən , ˌnəʊn- ]■ noun a person between 90 and 99 years old.OriginC19: from L. nonagenarius (based on nonaginta 'ninety') + -an . Concise Oxford English vocab. Сжатый оксфордский словарь английского языка. 2004