Octogenarian n. : A person eighty years, or more, of age.

Example:
Why is a person in their 80s called an Octogenarian?

Taxonomy
ageing, theory, lifespan, society, Gerontologist, health, cells, Misrepair, mortality, senescence, damage, disengagement theory, organisms, telomeres, adult, decline, genes, populations.

Defination from the web:
Octogenarian) Jump to: navigation, search. This article is about human ageing. ... Octogenarian. 80 to 89. Nonagenarian. 90 to 99. Centenarian. 100 to 109. Supercentenarian. 110 and older. People from 13 to 19 years of ...