septuagenarian
From Longman Dictionary of Contemporary Englishseptuagenariansep‧tu‧a‧ge‧nar‧i‧an /ˌseptʃuədʒəˈneəriən $ -ˈner-/ noun [countable] OLD/NOT YOUNGsomeone who is between 70 and 79 years oldOrigin septuagenarian (1700-1800) Latin septuagenarius “containing seventy”, from septuaginta “seventy”