| Acronym | Meaning |
| AVS | Acid Volatile Sulfide |
| AVT | Arginine Vasotocin |
| AWBERC | Andrew W. Breidenbach Environmental Research Center (US EPA) |
| AWCC | Active Well Coincidence Counter |
| AWFCO | Automatic Waste Feed Cutoff |
| AWG | American Wire Gauge |
| AWG | Arrayed Waveguide Grating |
| AWI | Air Water Interface |
| AWJ | Abrasive Waterjet |
| AWM | Abrasive Waterjet Machining |
| AWM | Average Wave Function Method (in Calcns. On Scattering) |
| AWMA | Air And Waste Management Association |
| AWPCF | Air And Water Pollution Control Facilities |
| AWQC | Ambient Water Quality Criteria |
| AWRA | American Water Resources Association |
| AWRE | Atomic Weapons Research Establishment |
| AWRG | Acid Waters Review Group (UK) |
| AWS | American Welding Society |
| AWSAR | Annual Whole Sludge Application Rate |
| AWT | Advanced Wastewater Treatment |
| AWWA | American Water Works Association |
| AWWARF | American Water Works Association Research Foundation |
| AXAF | Advanced X-ray Astrophysics Facility |
| AXS | Anomalous X-ray Scattering |
| B/F | Bag Filter |
| B1B | (coulomb) Boundary-corrected First Born (for Scattering) |
| B2B | Boundary(-corrected) Second Born (for Scattering) |
| B3LYP | A Density Functional Method Due To Lee |
| BA | Best Atom (basis Set) |
| BA + P | Best Atom + Polarization Function |
| BAAQMD | Bay Area Air Quality Management District |
| BABB | Back Arc Basin Basalt |
| BABE | Bio-Augmentation Batch Enhanced |
| BAC | Bacterial Artificial Chromosome |
| BAC | Biological Activated Carbon |
| BAC-MP4 | Bond-additivity-corrected Moeller-Plesset 4th-order Perturbation |
| BACER | Biological And Climatological Effects Research |
| BACM | Best Available Control Measure |
| BACR | British Association For Cancer Research |
| BACT | Best Available Control Technology |
| BADGE | Bisphenol A Diglycidyl Ether |
| BADGER | Bay Area Digital Geo-Resource |
| BADT | Best Available Demonstrated Technology |
| BAEP | Brainstem Auditory Evoked Potentials |
| BAER | Brainstem Auditory Evoked Response |
| BAF | Bioaccumulation Factor |
| BAF | Biological Aerated Filter |
| BAFF | B-cell Activating Factor |
| BAGI | Backscatter Absorption Gas Imaging |
| BAHC | Biospheric Aspects Of The Hydrological Cycle |