when i was a kid. however, a 'tank top' to a brit (of a certain age anyway!), is a sleeveless jumper like so....
what you call a tank top we call a vest.
what you call a vest, we call a waist coat.
what we call a jumper, you call a pullover. but then again.. we do too! and sweaters. so we've got that in common at least.
to be honest. i've never really known the difference between a jumper, a pullover or a sweater. i'm sure there is one though.
oh, and we call pants, trousers, but also pants... i'm confused now