A sexual act in which blue slurpee, soft drink or food dye is placed into a menstruating vagina. The subsequent period blood which comes forth, along with the blue drink is known as the blue moon, due to the blue colour and the period happening once a month, or moon.
Steve: Shana told me she was on her period last night, so I decided to give her a blue moon.
Jay: Cool digs man.
Jay: Cool digs man.
by CHOLERA MAN January 02, 2010