Door

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.

Any flap, etc. that opens like a door.

A non-physical entry into the next world, a particular feeling, a company, etc.

A software mechanism by which a user can interact with a program running remotely on a bulletin board system.

To cause a collision by opening the door of a vehicle in front of an oncoming cyclist or pedestrian.