Breakup define

After a breakup, or fight, one person (usually the petty one who gets upset they got called out on their douchyness) passive-aggressively defines the other's name and people they are jealous. They usually use a profile name for themself that they narcissisticly believe is clever and thinking to themselves "You'll Never Know".

Childishly defining someone as a means to get back at them while avoiding confrontation.

Something an ex does to retaliate against the other because they know the other is too good for them and they have to covertly attack them to sooth their hurt feelings when they themselves are the con artist who took advantage of the other's amazingness.

You'll never know I breakup defined you and him.

Lol, he narcissisticly breakup defined me because he's too much of a coward to own up to his horribleness and passive-aggressively attacking me on Urban Dictionary makes him feel like a big man.