| Abbreviation | Definition |
|---|---|
| AMD | Acid Mine Drainage |
| AMOSITE | Asbestiform Mineral - Cummingtonite-Grunnerite |
| AMSL | Above Mean Sea Level |
| ANCZ | Andaman and Nicobar Islands Coastal Zone |
| ANSI | Areas of Natural and Scientific Interest |
| ANSS | Advanced National Seismic System |
| AOV | Atlantic Ocean Volcanism |
| APD | Application for Permit to Drill |
| APGP | Alexandria petroleum Geology program |
| APLS | Advantage Porosity Logging Service |
| APM | Advanced Power Mangement |
| APT | Advanced Plume Treatment |
| APT | Australasia Pacific Thrust |
| APTR | APpalachian TRail |
| ARD | Acid Rock Drainage |
| ARM | anhysteretic remanent magnetization |
| ASF | Alaska Satellite Facility |
| ASOS | Automated Seismological Observation System |
| ASR | Alkali Silica Reactivity |
| ASR | Aquifer Storage and Recovery |