Definition of "octogenarian"

Mama was by no means the only grandma present, for the octogenarians had turned out en masse from their huts and lean-tos and were paddling about, diving and splashing as unconcernedly as though they really belonged in the sea rather than on land.

1929, Robert Dean Frisbee, The Book of Puka-Puka (republished by Eland, 2019; p. 75f; emphasis in original)

Finsbury Park station, one of the most important L.N.E.R. suburban junctions, is now an octogenarian.

1941 October, “Notes and News: Finsbury Park Station”, in Railway Magazine, page 466

To replace logarithmic tables with natural tables required some time. This seems like a modern age, yet I am not an octogenarian and I can remember the dying gasp of the logarithmic table as the standard method of computation. I have seen the desk calculator become a necessary instrument for every scientist who is doing quantitative work.

1951, IBM Corp., Proceedings, Computation Seminar, page 13