1) Being at least 100 years old 1) Old 2) Oldster 3) Veteran 
A centenarian is a person who lives to or beyond the age of 100 years. Because average global life expectancies are less than 100, the term is invariably associated with longevity. A supercentenarian is a person who has lived to the age of 110 or more, something only achieved by about one in 1,000 centenarians. Even rarer is a person who has lived...
• (n.) A person a hundred years old. • (a.) Of or relating to a hundred years.
[Noun] Plural form: centenarians. A person who is 100 years old or more.
Cen`te·na'ri·an adjective Of or relating to a hundred years. -- noun A person a hundred years old. 
Centenarian: Someone who is 100 or more years old. Someone 110 years old and over (no upper limit) may also be referred to as a supercentenarian. See also: Age by decade.
[adj] - being at least 100 years old 2. [n] - someone who is at least 100 years old
centenarian Someone who is in his/her hundreds; a person who is one hundred plus years old.
adjective being at least 100 years old
pertaining to or having lived 100 years.