90 Day Rule Share definition Flag When two people who are dating or "talking" officially go without sex for the first 90 daya of their relationship. Man, Becky said she does the 90 day rule.Whats that?No sex for 90 days!Good luck, buddy! 90 Day Rule by chemistry_425 August 22, 2016 0 0 Get merch Get the 90 Day Rule mug. Buy Now — $32.95 See more merch