BDSB Share definition Flag "Big, dirty, slut bag." Refers to an unappealing female, usually of a large frame and always promiscuous. Person x: "Look at that grenade all over that dude!" Person y: "She's a total bdsb." BDSB by gardzi January 20, 2011 0 0 Get merch Get the BDSB mug. Buy Now — $32.95 See more merch