nonagenarian
adjective/ˌnɒnədʒəˈneəriən/, /ˌnəʊnədʒəˈneəriən/
/ˌnəʊnədʒəˈneriən/, /ˌnɑːnədʒəˈneriən/
- between 90 and 99 years old
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nonagenarian
Definition of nonagenarian adjective from the Oxford Advanced Learner's Dictionary