water based lubricant used to fuck through the butt.
It has a thick consistency and a tendency to dry out during use, but can be "reactivated" by the addition of saliva or more water. Not recommended for ingestion, it has a sweetish taste, so as to not interfere with oral sex.
Woman: never through the butt. that hurts! the ass is not lubricated!
Man: Oh, common baby! I'll use some K Y to make it easier!