High Altitude Performance 
Hazardous Air Pollutant 
Harbor Assistance Program 
Hardware Allocation Panel 
Hazardous Air Pollutants 
hazardous air pollution 
High Altitude Platform 
Host Access Protocol 
Housing Assistance Payments 
humanitarian assistance program 
haemagglutinin/protease 
haptoglobin 
Harald's Archiver Programm 
Hardness Assurance Plan 
Harmonization Array Pedestal 
Hawaii Assessment Program 
hazard analysis process 
Health Alliance Plan 
heat-stable alkaline proteinase 
heavy atom perturber 
Helicopteros Aero Personal 
hepatic arterial phase 
hepatic arterial-dominant phase 
high alcohol preference 
High Altitude Program 
high available phosphorus 
high average power 
High-Altitude Photography 
High-Altitude Probe 
High-speed Arithmetic Processor