The acronym ARPA has several meanings:

• It is the former abbreviation of a U.S. military organization now known as the Defense Advanced Research Projects Agency (DARPA).
• On the Internet, it stands for Address and Routing Parameter Area: see .arpa.
• Automatic Radar Plotting Aid: see radar.

Also:

• The Arpa is a river in Armenia.
• Also an acronym for the Arkansas Rifle and Pistol Association, the group that lead the fight for shall issue concealed carry in Arkansas.