I imagine “jumper” will never become a true, proper Not One-Off Britishism. That’s partly because it has (as I understand it) a precise American equivalent, “sweater,” and partly because, in the U.S., “jumper” refers to a different kind of garment entirely. (In Wikipedia‘s words: “a sleeveless, collarless dress intended to be worn over a blouse, shirt, T-shirt or sweater.”) Thus the few times the word been mentioned on this site have been novelties, such as Andy Murray’s Christmas sweater (type “jumper” in the search bar at right to see the others).
What I have to share today is the closest I’ve seen to actual American use, but even it has some special circumstances. It’s an article published in yesterday’s edition of the Philadelphia Inquirer.
What are the special circumstances? Let me count them:
- The article is datelined “London” and is about stuff that happened in England; Princess Diana herself would probably have called the garment a jumper. So using the word in the article has a certain logic to it.
- “Sweater” was used in the headline, the lede, and about a half-dozen times in article, so the two “jumper”s could be seen as elegant variation.
- The writer of the article, Jill Lawless, is Canadian and has been based in England for a good amount of time.
Even so, it’s not nothing.
notoneoffbritishisms.com 
I recall the first time I heard the US meaning of jumper. I was at a science fiction convention in the UK and an American woman was asking about a line in a story she had read in which a woman had put on a jumper and a skirt, which she found confusing. The British people present explained to her what a jumper was and she gave the American meaning – a dress with a bib top designed to be worn over a blouse. In the UK that would be a pinafore dress (not to be confused with a pinafore. Later, a friend who did dressmaking said that a many dress patterns were printed in the US, that was well known to dressmakers.
However, I have seen Americans use jumper to mean a combination shorts and top, which seems to be also called a romper.
In some contexts, what Americans call a jumper would be referred to as a “gymslip”.
In England I think pullover, jersey, jumper and sweater as well some regional variations are all used for this garment. We often read here that X is THE American word for something that British English has more than one word for.
I don’t know, Ben; this one seems like just a context usage to pep up the text a bit. She’s calling it what the listing probably calls it. Meanwhile, one of my sons, whose British mother always calls sweaters jumpers, calls any pullover garment a “sweater.”
Reminds me that in ice hockey, the jersey is often referred to as a sweater, presumably originating in Canada.
Unrelated to this specific potential NOOB, but very NOOBy, today’s largest headline in the (print edition) of the Washington Post is the unfortunate, “Biden to allies: Don’t go wobbly.”
See https://notoneoffbritishisms.com/2018/06/11/go-wobbly/
Incidentally, I think in British English, woollen jumper or woolly jumper sounds more idiomatic.
And many papers outsource copy-editing to places like Australia, where kangaroos aren’t the only jumpers. (Although they’re probably more “hoppers.”)
Old joke when I was at school in the sixties (in the UK):
What do you get when you cross a sheep with a kangaroo?
A woolly jumper.
Good one!
Don’t forget the dark side meaning: someone who voluntarily defenestrates….
In British electrical terms a ‘Jumper’ is a short piece of wire which connects two adjacent electrical terminals -either to extend a common electrical feed or occasionally to bypass a limiting device for testing purposes.
It may also be termed a ‘shorting strip’…….
Not sure if this meaning crossed the Atlantic intact!
Yes, that “jumper” is used in U.S. as well.