octogenarian
🇺🇸
/ˌɑːktədʒəˈneriən/
🇬🇧
/ˌɒktədʒəˈneəriən/
An 80 to 89-year-old person.
My grandmother, an octogenarian, is more active than many younger people I know.
我的祖母,一個八旬老人,比許多我認識的年輕人更活躍。