What does "un-ungrounded" mean here? It seems like it has something to do with "grounded" but I don't get about "un-ungrounded" though.
You are correct, this is related to "grounded". The adjective "grounded" is usually used to refer to a child or young person who is not allowed to go out as a punishment for something. Therefore to be "ungrounded" would simply mean that a previous decision to "ground" a child has been changed. "Un-ungrounded" therefore means that an early decision to no longer "ground" someone has changed back and they are "grounded". It is key to note that "un-ungrounded" is not a real phrase and is being used mainly for comedic effect. Ex: I got grounded because I stayed out late. Ex: My mom grounded me because I failed my exam.