I might not request a BUR outright like I usually do, but I can't see exactly what tag is meant for when we already have a whole encyclopedia of tags dedicated exclusively to breasts and their level of exposure:
breasts out, one breast out, areola slip, nipple slip, downblouse, underboob, sideboob, backboob, bursting breasts
For clothes openings/gaps: center opening, cleavage cutout, button gap, plunging neckline
The wiki is not very descriptive either and it's only linked in another two tags, so it makes me think the tags mentioned above and this tag were created independently and that fact possibly went unnoticed, any thoughts?