A one-piece bathing (or tanning) suit for women:
1. just a bottom piece, hence a
euphemism for topless
2. a bikini whose top and bottom pieces are connected by cloth either a) on the front, b) the back or c) both, but with the kidney area uncovered
3. much like #2 but with a neckholder and no strings
on the back
4. jokingly for a classic swimsuit which covers much of the torso or even for a burkini
This can lead to misunderstandings,
obviously.