A rushed marriage that crumbles to pieces after a couple of months. Derived from a "shotgun wedding" where the bride and groom are forced to marry due to an expectant child. In a reverse shotgun wedding, the couple is rushed amongst themselves and the whole thing blows up in their face.
Person 1: Did you hear about Kent's marriage? What a disaster!
Person 2: Well what do you expect? Everyone knew it was a reverse shotgun wedding.