A piercing, often a Nipple Piercing, which is structurally important to an outfit. This can be due to the clothes being held on with a Piercing Through Clothes, or by the clothing hanging off of a Ring Piercing or similar.
Contrast Piercing Pull when a piercing is being pulled on externally, but is not supporting something self-contained to the wearer. Also contrast Linked Piercing or Nipple Jewelry, Nipple Bells, etc. where the piercing is supporting a relatively small object or decorative accent, rather than some or all of a larger piece of clothing.