| 22K | 22 Karat | |
| A | Australian | |
| A-GPS | Assisted Global Positioning System | |
| A-GPS | Augmented Global Positioning System | |
| AADC | Australian Antarctic Data Centre | |
| AAG | Association of American Geologists | |
| AAOD | Australian Age of Dinosaurs | |
| AAPG | American Association of Petroleum Geologists | |
| AARS | Asian Association of Remote Sensing | |
| AASR | Annual Aquaculture Statistics Report | |
| ABFZ | Angola Benguela Frontal Zone | |
| ABFZ | Azores Bank Fracture Zone | |
| ABFZ | Agua Blanca Fault Zone | |
| ABP | Aegean Blue Pearl | |
| AC | American Coast |
|
| ACE | Amethyst Contrast Enhancer | |
| ACE | After the Common Era | |
| ACH | Aki, Christoffersson, and Husebye | |
| ACI | l’Association Cartographique Internationale | |
| ACM | Autonomous Crack Monitoring | |
| ACP | Active Control Point | |
| ACR | Angelo Coast Range | |
| ACRC | Australian Crustal Research Centre | |
| ACRR | Angelo Coast Range Reserve | |
| ACWI | All Country World Index | |
