Definition of door:
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 room that is entered via a door; "his office is the third door down the hall on the left"