资料来源 : Free On-Line Dictionary of Computing

dangling pointer
     
         A reference that doesn't actually lead anywhere.
        In {C} and some other languages, a pointer that doesn't
        actually point at anything valid.  Usually this happens
        because it formerly pointed to something that has moved or
        disappeared, e.g. a {heap}-allocated block which has been freed
        and reused.
     
        Used as jargon in a generalisation of its technical meaning;
        for example, a local phone number for a person who has since
        moved is a dangling pointer.
     
        [{Jargon File}]