a swinging or sliding barrier that will close the entrance to a room or building or vehicle
"he knocked on the door"
"he slammed the door as he left"
the entrance (the space in a wall) through which you enter or leave a room or building; the space that a door can close
"he stuck his head in the doorway"
anything providing a means of access (or escape)
"we closed the door to Haitian immigrants"
"education is the door to success"
a structure where people live or work (usually ordered along a street or road)
"the office next door"
"they live two doors up the street from us"
A portal of entry into a building, room, or vehicle, 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.
"She pushed against the heavy wooden door with her shoulder until it swung inward on its hinges, revealing the dark hallway beyond."
In plain English: A door is a hinged panel that opens and closes to let people or things move between rooms or outside.
"Please close the door behind you when you leave the room."
Usage: Use "door" to refer to any rigid panel hinged at one side that swings open to provide entry or exit for a building, room, or vehicle. You can also use it metaphorically to describe an opportunity, such as saying someone has opened a door to new possibilities.
To cause a collision by opening the door of a vehicle in front of an oncoming cyclist or pedestrian.
"The motorist was ticketed for dooring after he swung his car door open and clipped the bicycle rider passing behind him."
In plain English: To door someone means to kick them out of a place.
"The wind slammed the door shut behind him."
Usage: Do not use "door" as a verb; it is strictly a noun referring to a hinged barrier for entering or leaving. If you mean to cut someone off by opening a car door, simply state that action rather than inventing a new verb form.
The word "door" comes from Old English doru, meaning "gate," and has been used in English since the Middle Ages. Its roots trace back through Proto-Germanic and Proto-Indo-European to an ancient concept of a doorway or entrance.