GERK and gerk
n. an elderly simpleton; an old nerd. (Acronym. From geriatric and jerk.)Old man Johnson is a real GERK—ill-tempered and rude.A couple of gerks sat on the park bench, snoozing.
golden-ager
n. an old person; a senior citizen.The golden-agers sat on the benches and chatted.When I'm a golden-ager, I'm going to have a part-time job.
old-timer
n. an old person; an old man. (Also a term of address.)Hey, oldtimer, how's it going?Ask that old-timer over there if it has always been this bad around here.