What a confusing word! I thought teeshirt, which got short shrift from Duo. To me jerseys are woolly jumpers, which implies a thickness and warmth not typical of a maillot. "Close-fitting long-sleeved undershirt" seems very long winded. Perhaps we should just call it a maillot and have done with it?
I am from the UK and to me a jersey is a woolly jumper - although now a very old fashioned way of describing a jumper. In answer to your question I looked at online cycle shops and it appears cycle tops (long and short sleeved) are called jerseys now - possibly the influence of the tour de france. But in the UK for normal casual wear we would call it a t-shirt and maybe specify whether long or short-sleeved. They can also be called football or rugby shirts - but would usually be in team colours. I think, for most non cycling enthusiasts, either side of the altlantic, this is confusing. If a maillot only refers to a tight fitting lycra top worn for sports, the sentences should be in context. And DL should accept vest and T-shirt.
"Jersey" is a word in broad use in the U.S. for apparel worn on the top half of the body when engaged in sporting endeavors, particularly team sports. They need not be tight-fitting.
For instance all the following are familiar collocations to me:
- hockey jersey
- baseball jersey
- basketball jersey
- soccer jersey
- football jersey (and "maillot de football américain" yields applicable Google results for those of us who use "football" to refer to that sport)
Those are all links to the relevant Reverso entries. "maillot" seems to show up for all of them, although there are alternatives, and some of them are far from rich in usage examples.
I'm unsure if "maillot" is used to refer to T-shirts in general (e.g. outside the specific context of sports or undershirts). I haven't seen that listed in the French-English dictionaries I checked, e.g. Larousse. And at least this French-language dictionary seems to line up with the undershirt / sports / dance categories: (although adding that apparently it also means "swaddling clothes").
If it's red, it's probably a jersey. The leader of the Tour de France famously wears the maillot jaune, for instance, a yellow bike jersey. It also means "undershirt" (American), which I guess is "vest" in British English, "maillot de corps" apparently if you want to specify. It's also seemingly used as a short form of "maillot de bain" (swimsuit) and is also the kind of thing gymnasts/dancers/figure skaters wear.
One important thing is to find out what FRENCH people consider in maillot. That done, we can all report our own pet name for that garment, and report it to the mods.
So Google the images for maillot and decide what you want to call it in English. Clearly for most Americans the answer will be "jersey".