When you all say "tank top", what do you mean?

In the UK, a tank top is like a sleeveless knitted jumper/sweater and I'm sure you don't mean that.

Do you mean those little tops with spaghetti straps?
Do you mean what we call a vest top, but others might describe as a singlet-style top?
Do you just mean sleeveless?

If you link to some pictures of what you mean, that would be a great help.