When a roommate moves out, and then completely cuts off all communication with ex-roommates, ignoring all phone calls, text messages, emails, and smoke signals sent from said roommates.
Regardless of whether the individual moves out on good or bad terms, you will never be able to get in contact with this individual ever again.
Roommate 1: Hey so we're still getting mail for Maggie, can you let her know?
Roommate 2: Uh, no, she pulled a Maggie Moveout, so we will literally never hear from her again...
Roommate 2: And dude, it's weird anyways, because you and I have moved into a new apartment, and her mail from the old apartment we shared with Maggie *followed us here.*
Girl 1: This isn't Diggens! What happened to the underbite dog?
Guy 1: IDK, I got blindsided by a Maggie-moveout, and I haven't seen Diggens since. I hope he's O.K. This is my new roommates dog, Roxy.
Girl 1: Oh, what a cute Boxer! Come inside and grab a drink.