Meaning

• To close, terminate, or end.

  "They are planning to shut down the entire building at the end of the month."

• To turn off or stop.

  "It's a good idea to shut down the machine before you leave."

• To emotionally withdraw into oneself as a defense mechanism; to block out external stressors.

  "I can't talk to him about a certain thing; he just shuts down anytime I try."

• (auto racing, car culture) To pass (another vehicle), especially quickly.