Definition of "door"

noun:
- A portal of entry into a building or room, consisting of a rigid plane movable on a hinge. Doors are frequently made of wood or metal. May have a handle to help open and close, a latch to hold the door closed, and a lock that ensures the door cannot be opened without the key.
  
  from Wiktionary, Creative Commons Attribution/Share-Alike License
- Any flap, etc. that opens like a door.
  
  from Wiktionary, Creative Commons Attribution/Share-Alike License
- A non-physical entry into the next world, a particular feeling, a company, etc.
  
  from Wiktionary, Creative Commons Attribution/Share-Alike License
- A software mechanism by which a user can interact with a program running remotely on a bulletin board system.
  
  from Wiktionary, Creative Commons Attribution/Share-Alike License
verb:
- To cause a collision by opening the door of a vehicle in front of an oncoming cyclist or pedestrian.
  
  from Wiktionary, Creative Commons Attribution/Share-Alike License