(noun) Relationship term used about a person soon to become a former boyfriend or girlfriend. Usually used when a break-up is (or should be) imminent.

Pre-ex refers to your ex boyfriend/girlfriend before the break up. Many people get confused when someone refers to their ex if they are talking about before or after the break up.

If a person says, "My ex burned my house down" you wouldn't know if the ex boyfriend/girlfriend burned the house down while they were still dating and that's why they broke up or if they broke up and then the ex boyfriend/girlfriend burned the house down.