blood sissy Share definition Flag Two women who when on their periods engage in the act of eating eachother other out for hygiene and pleasure. Commonly heard in a sentence along the lines of... "Ur lyk fam grl. Luv you blood sissy <3" blood sissy by bobilly March 31, 2015 0 0 Get merch Get the blood sissy mug. Buy Now — $32.95 See more merch