To cease operations or turn off a machine or system. The factory will shut down for maintenance over the weekend.
To close a business or organization permanently or temporarily. The restaurant had to shut down due to financial difficulties.
To stop someone from expressing their opinion or to dismiss their ideas. He tried to voice his concerns, but the manager shut him down immediately.
To stop functioning or operating, often used in reference to a computer or electronic device. The computer will automatically shut down if it overheats.