door (Noun) — A swinging or sliding barrier that will close the entrance to a room or building or vehicle. ex. "he knocked on the door" ex. "he slammed the door as he left"
door (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. ex. "he stuck his head in the door"
door (Noun) — Anything providing a means of access (or escape). ex. "we closed the door to Haitian immigrants" ex. "education is the door to success"
door (Noun) — A structure where people live or work (usually ordered along a street or road). ex. "the office next door" ex. "they live two doors up the street from us"
door (Noun) — A room that is entered via a door. ex. "his office is the third door down the hall on the left"