Living in someone's head rent free. They are in your mind all the time and you are constantly thinking about them. All your thoughts are about them, and they have no idea. Usually happens when you have a big crush on someone
The phenomenon of Woolwicharsenal fans being completely obsessed with Spurs, constantly talking about them and generally thinking about Tottenham Hotspur all the time. Whilst therest of the world barely knows who the Woolwich even are
An insult commonly used on various 4Chan boards.
It insinuates that the person being insulted lives "rent free" with his or her parents, and thus must be a NEET with no life.
Note that when used, insults like this will often either completely shut down an argument or turn it into a rapid back-and-forth flame war, derailing it.
Living Rent free means that someone is always thinking about that thing or place for example
America and Christians live rent free In the minds of reddit