n 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
n 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
n anything providing a means of access (or escape)
we closed the door to Haitian immigrants education is the door to success
n 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
n a room that is entered via a door
his office is the third door down the hall on the left