6 month rule Share definition Flag After a couple has been dating for 6 months, it is now safe for them to have sex, and not regret it. "Mark and Jamie had sex!? But they forgot the 6 month rule! Oh shit!" 6 month rule by MMjr February 20, 2009 0 0 Get merch Get the 6 month rule mug. Buy Now — $32.95 See more merch