The word has a long and varied history. The current “usual sense” according to the OED is: “A person who receives a pension or stated allowance in consideration of past services or on account of injuries received in service; a retired person who receives a pension.” (“In earlier use,” the dictionary adds, “frequently applied to disabled soldiers and sailors of the Chelsea Royal Hospital and Greenwich Hospital.”)
Here’s what Google Books Ngram Viewer has to say about American and British use of the term (click on the image for a bigger view):
That is, sort of went back and forth in the 19th century, with notably more use in Britain in the 20th, but a pronounced dip there in the 21st. The OED citations are all British or Australian, with the exception of a quote from Herman Melville’s 1891 novella, Billy Budd: “The same thing was personally communicated to me now more than forty years ago by an old pensioner in a cocked hat, with whom I had a most interesting talk.” American use started falling off around then, slowly declining ever since.
I have the feeling — not backed up by the OED or other dictionaries I’ve consulted — that in Britain, “pensioner” might refer to a person who is no longer working but is not necessarily receiving a pension: what Americans would call a “retiree.” That’s suggested to me by the most recent OED citation, from Empire magazine in 1997: “Every other Thursday we do a golden oldies film club where we let pensioners come in for a pound.”
Bearing on the usage, probably, is the fact that in Britain and Europe, most retirees get pensions. In the U.S., by contrast, retirees generally receive modest Social Security payments but not pensions, which here are the offered (or not) by employers, not the government. They were once widespread, but as far back as 2008, only 13% of the workforce could expect to receive pensions; the number is certainly smaller now.
As a result, American uses of “pensioner,” what few there are, tend to refer specifically to people getting (often particular) pensions, not to a general class. For example, these quotes, all from 2020:
- “The chief investment officer of one of the country’s biggest public pension funds said the government response to the coronavirus should be focused on supporting unemployed workers, not stocks owned by pensioners.”–CNBC
- “[McClatchy’s] acquisition of Knight Ridder loaded it with billions of dollars more of crisis, and its pension thing is unsustainable. They say they have 28 pensioners for every employee.”–National Public Radio
- “A spokeswoman for Scott Stringer, the New York City comptroller who sits ex officio on the boards of pension funds serving teachers and other workers, said, ‘We are troubled by these reports, and we are closely monitoring the situation in accordance with our fiduciary duty and to protect the interests of our pensioners.'”–New York Times