Wiktionary
quadripoint
n. a point at which four borders meet.
Wikipedia
Quadripoint
A quadripoint is a point on the Earth that touches the border of four distinct territories. The term has never been in common use — it may not have been used before 1964 when it was possibly invented by the Office of the Geographer of the United States Department of State. The word does not appear in the Oxford English Dictionary or Merriam-Webster Online dictionary, but it does appear in the Encyclopædia Britannica, as well as in the World Factbook articles on Botswana, Namibia, Zambia, and Zimbabwe, dating as far back as 1990.