GAPA meaning in General ?

Boeing's Ground-to-Air Pilotless Aircraft (GAPA) was a short-range anti-aircraft missile (SAM) developed in the late 1940s by the US Army Air Force, and then the US Air Force after 1948. It was given the reference number SAM-A-1, the first Surface-to-Air Missile (SAM) in the 1947 tri-service designation system. By 1950 over 100 test rockets had been launched using a variety of configurations and power plants, with one launch in 1949 setting the altitude record for a ramjet powered vehicle at 59,000 ft (18,000 m).

GAPA faced strong competition from the US Army's Nike missile system, and was eventually cancelled in favour of Nike for deployment. The GAPA work was later re-used by the Boeing and Project Wizard team at the Michigan Aeronautical Research Center to develop a much longer-ranged missile, the CIM-10 Bomarc. Bomarc would end up competing with the Army's Hercules missile, and was deployed only in small numbers.