Persona = Person, individual.
non = not
Grata = welcome, allowed, etc.
If you are Persona non Grata it means you are no longer welcome somewhere, you stink, you are scum, you should be shot on sight (and in some places will be). It means you are an embarassment, someone to be shunned. Even a Leper colony would turn you away. Ok, maybe not. But it would be a close thing.
