NWF Renim said:
This leaves us only with the restriction that the nipple then shouldn't be shown. If we follow this definition, then that would mean that in the image there will have to be something like clothing or hair that is covering the breasts/nipples.
I never bothered bringing it up on the forum, but I created an areola_slip tag for that a while back. I left it singular because, as you state, it's possible for only one areola to be visible. It's still comparatively rare for only one to be visible, though.