| Acronym | Definition |
|---|
| HA | Hands (Front Page Sports Football '95 et al) |
| HA | High Availability |
| HA | Highly Available |
| HA | Home Agent |
| HA | Heart Attack |
| HA | Hospital Authority |
| HA | Housing Authority |
| HA | Home Address |
| HA | Haiti |
| HA | La Habana (postcode, Cuba) |
| HA | Home Alone |
| HA | Headache |
| HA | Hawaii (old style) |
| HA | Highways Agency (England) |
| HA | Health Affairs |
| HA | Hectares |
| HA | Home Automation (residential housing controls) |
| HA | Health Assessment |
| HA | Hydrogen Alpha |
| HA | Health Administration |
| HA | High Altitude |
| HA | Hells Angels |
| HA | Harrow (postcode, United Kingdom) |
| HA | Human Anatomy (college course) |
| HA | Humanitarian Assistance (US DoD) |
| HA | Historical Association (various organizations) |
| HA | Hyaluronic Acid |
| HA | Humanitarian Assistance |
| HA | Half-Assed |
| HA | High Authority |
| HA | Heritage Area (various locations) |
| HA | Hydroxyapatite |
| HA | Hospital Acquired (Infection) |
| HA | Hidden Ability (Pokémon) |
| HA | Hazard Analysis |
| HA | Hawaiian Airlines (IATA airline code) |
| HA | Hippocampal Atrophy (neurology) |
| HA | Hazard Assessment |
| HA | Health Advisory |
| HA | Hemolytic Anemia |
| HA | Humic Acid |
| HA | Holding Area |
| HA | Hauptabteilung (German) |
| HA | High Assurance |
| HA | Heavy Armor |
| HA | Hepatic Artery |
| HA | Housing Allowance |
| HA | Histocompatibility Antigen |
| HA | Halmahera |
| HA | Hour Angle |
| HA | Heterocyclic Amine (food mutagen) |
| HA | High Ambient (temperature limit) |
| HA | Hospitality Association |
| HA | High Achiever |
| HA | Hemaglutinin (glycoprotein on influenza virus) |
| HA | Highways Act 1980 (UK) |
| HA | Hazardous Area |
| HA | Height-For-Age |
| HA | Honorary Alumnus |
| HA | Hahnium |
| HA | Healthy America |
| HA | Hepatitis-Associated |
| HA | Home Assignment |
| HA | Half Adder |
| HA | Hybrid Algorithm |
| HA | Hemagglutination Assay |
| HA | Haute Activité (French: High Activity; radioactivity) |
| HA | Hostile Aircraft |
| HA | Hydrocephalus Association |
| HA | Hypnotherapy Association |
| HA | High-Alarm |
| HA | Household Activity |
| HA | Haight-Asbury |
| HA | Harmonic Approximation |
| HA | Heidelberg Appeal |
| HA | Hybrid Amplifier |
| HA | Hub Architecture |
| HA | Hexenyl Acetate |
| HA | Hearing Assistant |
| HA | Adopted in the House (approved business of the House of Representatives, North Carolina) |
| HA | Hatch Act of 1887 |
| HA | Hippocampal Asymmetry |
| HA | Hardness Assurance (radiation) |
| HA | Harmonic Analyzer |
| HA | Hall Angle |
| HA | Hospitalman Apprentice (US Navy rating) |
| HA | Hyper-Androgenism |
| HA | Halifax Academy (Roanoke Rapids, North Carolina) |
| HA | Hack Addict (eZine) |
| HA | Hit Avoidance |
| HA | Hit Assessment |
| HA | Hydraulic Association (UK) |
| HA | Hull Array |
| HA | Heavy Assist (nursing) |
| HA | Homelan Alliance (gaming clan) |
| HA | Hanford Operations Office (Department of Energy) |
| HA | Howey Academy (Florida) |
| HA | Hipuric Acid |
| HA | Heyting Arithmetics |
| HA | Heterodyne Amplifier |
| HA | Hersteld Actief (Dutch) |
| HA | Hard Copy Text or Drawing |