A fork of Rural Dictionary
The person who used to be, but is no longer your next door neighbor.
I invited my ex-door neighbor from California; I hope you don't mind.
Someone you know who used to live right next to you.
Tim (to Alex): What's up? Tom (to Tim): Do you even know that dude? Tim (to Tom): Heck yes, he's my ex-door neighbor, we used to hang out sometimes.
The person who used to live next door to you, but no longer does, either because they moved away or you did.
Susie just moved away, I guess that makes her my ex-door neighbor.