UK "vest", as in US "undershirt", or US "vest", as in UK "waistcoat"?
So this is not the sleeveless garment on top of a shirt or blouse? What is that?
That could be a couple of things, but:
But what we call a "vest" in North America is a "waistcoat" in British English. I think this is causing some confusion.
I can think of at least 3 possibilities:
A tank-top if knitted.
A body-warmer if padded and zipped.
A waistcoat if it's the sort of garment that would be worn with a formal suit.
....whereas for me, as a 'uk'-english speaker, a vest is definitely a garment worn underneath other clothes, and not generally intended to be seen.