To keep unwanted people out of a safe area so that they are unable to escape the consequences of having made their own area fatally unliveable, with the implication being that to let them in would only be to share their fate.
After the French run out of food, we'll hold the door shut in England until it all goes quiet.
Someone who is addicted to obtaining money and building wealth. A money addict and fanatic. Breadheads often work more than one full-time job, and some even participate in illicit activities to "obtain the bread".