one breast out
When one breast is exposed while the other remains covered or confined by clothing. See breasts out for when both breasts are exposed.
If the exposed breast is only partially exposed, the entire nipple and areola should be visible.
This tag most often accompanies open shirt, wardrobe malfunction, shirt pull, bra pull, or similar tags, but it is not a necessity.
Remember that just because you cannot see the other unexposed breast, it does not implicitly mean this tag should be used. The unexposed breast could simply be blocked from view by the persons arm or hand, or the body of another character in the picture.