A blueberry facial is the act of putting a large amount of blueberries in your partner's mouth, and then giving them a facial.
After having sexual intercourse, one partner might decide to reward their partner with a facial of the blueberry variety. A blueberry facial is widely used by the gay comunity.
Cube slave 1: "Dude, I'm soooo damn bored..."
Cube slave 2: "You should take up facial spelunking."
Cube slave 1: "Man, I'm so past that, I've beenbooger bombing you for hours..."