If a window or a house is shuttered, it has shutters — those wooden or metal covers on the outside of a window — or those covers are closed. That is the picture the word started with. Though actually, the way you will meet it most is about shops, factories, and restaurants. When a shop is shuttered, the metal door at the front has been pulled down. Sometimes that only means closed for the night. Very often, especially in the news, it means the business has stopped for good: nobody works there any more. Writers like this word after a storm, a war, or a bad year for money. It feels a little more formal than just saying closed. At home, people usually say they closed the shutters, not that the window is shuttered.