[countable] a piece of wood, glass, etc. that is opened and closed so that people can get in and out of a room, building, car, etc.; a similar thing in a cupboard/closet a knock on the door to open/shut/close/slam/lock/bolt the door to answer the door (= to go and open it because somebody has knocked on it or rung the bell) the front/back door (= at the entrance at the front/back of a building) the bedroom door the door frame a four-door saloon car the fridge door Shut the door! Close the door behind you, please. The door closed behind him. in an unfair or indirect way He used his friends to help him get into the civil service by the back door.