| Abbreviation | Definition |
|---|---|
| ATCS | Active Thermal Convective System |
| ATFT | Affine Toda Field Theory |
| ATIP | Application Targeted and Integrated Photovoltaics |
| ATLAS | A Toroidal LHC Apparatus |
| ATLAS | Argonne Tandem Linac Accelerator System |
| ATMP | Advances in Theoretical and Mathematical Physics |
| ATS | Almost Time Symmetric |
| ATU | Accumulated Thermal Unit |
| ATWE | Annual Time Weighted Exposure |
| AUM | Arbitrary Unit of Mass |
| AVN | Accuracy Vanishing Now |
| B | Baryon |
| BALLD | Brief Alternating Laser Light Defolicalization |
| BARC | Bhabha Atomic Research Centre |
| BAS | Bulletin of the Atomic Scientists |
| BaVL | Barium Vapor Laser |
| BAW | Bulk Acoustic Wave |
| BB | Back Bombardment |
| BBN | Brains And Backbone Network |
| BBP | Breast And But Physics |