Referring to your ex (girlfriend, boyfriend, husband, wife) prior to your current ex (girlfriend, boyfriend, husband, wife). Similar to how Christmas Eve Eve is two days before Christmas.
Can also be extended out indefinitely, ie. ex ex ex would be the ex prior to the ex ex.
Bobby: Who was that?
Ricky: Oh, that's my ex ex. She's a real pain. My ex and I actually still get along.
a person whom one has remarried after divorce. An ex ex was one's ex-spouse in the past.
How are you getting on with your ex ex?