ICBM address n.
(Also `missile address') The form used to register a site with
the Usenet mapping project, back before the day of pervasive
Internet, included a blank for longitude and latitude, preferably
to seconds-of-arc accuracy. This was actually used for generating
geographically-correct maps of Usenet links on a plotter;
however, it became traditional to refer to this as one's `ICBM
address' or `missile address', and some people include it in
their sig block with that name.
(A real missile address would include target elevation.)