What does “persona non grata” mean? [closed]

Question

In Gossip Girl, there’s a line like this:

Spotted, Lonely Boy going from Teacher’s Pet to persona non grata in the pitter-patter of a heartbeat.

What’s persona non grata?

Answer 1

It means someone who is unwelcome, from the Latin meaning exactly that. It is usually used in a diplomatic sense, but has broadened to include any person who is unwelcome in any context or to any group.

When Anne showed up at her ex-husband's funeral, the family made her feel like persona non grata.

Answer 2

I assume this is a non-diplomatic usage of the word. From Wikipedia:

In non-diplomatic usage, referring to someone as persona non grata is to say that he or she is ostracized, so as to be figuratively nonexistent. In police circles, this often meant any officer who broke the Blue Wall by informing against fellow officers, e.g. testifying against officers who were corrupt. Frank Serpico was one real life example, while a cultural example is Paul Newman's character in Fort Apache, The Bronx, who informed on a fellow officer after witnessing him throw an unarmed man off a rooftop during a riot. On September 1, 2010 the Vice Mayors League of the Philippines-Cebu passed a resolution declaring former Miss Universe 1969, Gloria Diaz, persona non grata.