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.