Definitions of door:

• noun:   a swinging or sliding barrier that will close the entrance to a room or building or vehicle

  Example: "He knocked on the door"

• noun:   a room that is entered via a door

  Example: "His office is the third door down the hall on the left"

• noun:   a structure where people live or work (usually ordered along a street or road)

  Example: "The office next door"

• noun:   anything providing a means of access (or escape)

  Example: "We closed the door to Haitian immigrants"

• noun:   the entrance (the space in a wall) through which you enter or leave a room or building; the space that a door can close

  Example: "He stuck his head in the doorway"

• name:  A surname (very rare: popularity rank in the U.S.: #35939)