noun. 
                    A movable barrier of wood, metal, stone, or other material, consisting sometimes of one piece, but generally of several pieces framed together, commonly placed on hinges, for closing a passage into a building, room, or other inclosure.
                  
                
                  
                    noun. 
                    An opening for passage into or out of a building or any apartment of it, or any inclosure; a doorway.
                  
                
                  
                    noun. 
                    Hence—3. An exterior or public entrance-way, or the house or apartment to which it leads.
                  
                
                  
                    noun. 
                    Avenue; passage; means of approach or access, or of exit: commonly in figurative uses: as, the door of reconciliation; a door of escape.
                  
                
                  
                    noun. 
                    Near to; bordering on; very nearly.
                  
                
                  
                    noun. 
                    Hence, figuratively, quite gone; no more to be found; lost; irrelevant.
                  
                
                  
                    noun. 
                    Figuratively, to ruin one.