Anus areola that is exposed when a woman wears a thong and bends over. In other words, the darker colored skin around the bung that a woman might reveal while wearing a g-string.
Slightly different from an alternate definition that refers to the triangle patch of fabric or whale tail near the top of the thong, this varient is specific to exposed penumbra of flesh around the butthole which combined with buttfloss looks like an Eyepatch a pirate might wear.

the triangle of fabric in the back of thong underwear, referred to when it peeks out of the top of a woman's pants, named as such because of the two srings holding it up and the fact that it covers
"the brown eye"