preexisting condition

despite having a new girlfriend/boyfriend, sex with the ex is so good it must continue. Also known as Grandfathered in.

Guy 1: I cant go man I was up all night making sweet sweet love to Lisa.

Guy 2: Dude I thought you were seeing Veronica?

Guy 1: Lisa's a preexisting condition man! Shes Grandfathered in!!!

by ChiBlonde November 10, 2012

Pre-existing condition

An old flame you can’t help hooking up with periodically, regardless of either person’s relationship status.

Amy: I can’t believe you slept with Adam after the class reunion. He’s engaged and you have a boyfriend!

Lola: Hey it wasn’t my fault. Adam is a pre-existing condition.

by builtforspeed July 25, 2018