Rule Number 8 Share definition Flag Sex rule stating, "All women like it in the ass; some just don't know it yet." Can also be used as a verb. "My girlfriend and I proved Rule Number 8 last night; now she can't get enough!" Rule Number 8 by Blackbird Pilot September 1, 2009 0 0 Get merch Get the Rule Number 8 mug. Buy Now — $32.95 See more merch