1) Golden ager 2) Old person 3) Oldster 4) Senior citizen 
• (n.) A person who is seventy years of age; a septuagenary.
Sep`tu·a·ge·na'ri·an noun A person who is seventy years of age; a septuagenary. 
Septuagenarian: Someone in his or her seventies. See also: Age by decade.
[n] - someone whose age is in the seventies
septuagenarian 1. A person who is in his/her seventies. 2. Someone who is seventy to seventy-nine years old.
noun someone whose age is in the seventies