You already know the regular karma. When you do something bad, then that something bad will also happen to you. But this reverse karma is not the same, it works differently. When someone do something bad to you, someday you’ll do that bad thing to the other.
This is an example of reverse karma. I used to have a girlfriend, but she cheated on me, and then we broke up. Several years later i had another girlfriend, and i cheated on her. Of course we also broke up.
It’s not a vengeance. It’s not that i want to get even, because i did it unintentionally. That’s the different between regular karma and reverse karma. Either way, karma is a bitch. It’s fun, but still, it’s a bitch.