› a flat, usually rectangular, object that is fixed at one edge and is used to close the entrance to something such as a room, building, or vehicle, or the entrance itself: the front/back door We’d like to rent a four-door car. I’ll meet you at the main door of the library. Would you open/close/shut the door, please? The door to his bedroom was locked from the inside. Mom, there’s someone at the door (= outside the front door). › Door is also used to refer to a house or other building: Sam lives just a few doors away/up/down from us. They live next door to us (= in the house beside ours).