your-age-minus-seven-times-two
Derived from the half-your-age-plus-seven rule. Used to define the oldest that a romantic interest can be before the relationship is considered indecent. This rule is considered more accurate than the your-age-plus-half-your-age-minus-seven rule, which in some cases conflicts with the half-your-age-plus-seven rule.
Jackie and Dan were mutually attracted, but Jackie waited until she turned 21 to make a move on the 28-year-old Dan, thereby making it acceptable under the your-age-minus-seven-times-two rule.