going-away sex
When your significant other/partner is leaving for a long period of time (a vacation, business trip, going off to college) and you have sex right before they leave so they can have a final good memory of you before not seeing you for a while.
person 1: My girlfriend is about to go on vacation with her family and we spent the day before she left having going-away sex.
person 2: Radical dude.
person 2: Radical dude.