oldster, old person, senior citizen

an elderly person

• antediluvian — a very old (or old fashioned) person
• centenarian — someone who is at least 100 years old
• curmudgeon — a crusty irascible cantankerous old person full of stubborn ideas
• dodderer — one who dodders from old age and weakness
• dodo, fogy, fogey, fossil — (informal) someone whose style is out of fashion
• dotard — an oldster in his dotage; someone whose age has impaired his intellect
• has-been, back-number — someone who is no longer popular
• nonagenarian — someone whose age is in the nineties
• octogenarian — someone whose age is in the eighties
• old boy — a vivacious elderly man
• old man, greybeard, graybeard, Methuselah — a man who is very old
• old woman — a woman who is old
• septuagenarian — someone whose age is in the seventies
• sexagenarian — someone whose age is in the sixties

• adult, grownup — a fully developed person from maturity onward