Generally refers to a nipple which is slippery. Commonly used in S&M circles to describe a nipple which is difficult to attach objects to.
During our first S&M class, I couldn't clamp a clothespin on my girlfriends butternipples so I clamped it on her earlobe instead.
by butterman March 01, 2012
When an individual's nipples milk for a long period of time without getting wiped off leaving a buttery looking substance on the nipple and/or around the nipple
Sabbatha had ButterNipples while she was pregnant
by VomitCock May 27, 2017