septuagenarian

/S EH0 P CH UW0 AH0 JH AH0 N EH1 R IY0 AH0 N/
noun
  1. 1

    One who is between the age of 70 and 79, inclusive.

adjective
  1. 1

    Being between the age of 70 and 79, inclusive. In one's eighth decade.

  2. 2

    Of or relating to a septuagenarian.

Source: https://en.wiktionary.org/wiki/septuagenarian