| Acronym | Meaning |
| BAIR | Biological Atlas Of Insulin Resistance |
| BAL | Blood Alcohol Level |
| BAL | Broad Absorption Line |
| BAL | Bronchoalveolar Lavage |
| BALF | Bronchoalveolar Lavage Fluid |
| BALP | Bone Alkaline Phosphatase |
| BALQSO | Broad Absorption Line Quasi-stellar Object |
| BALR | Broad Absorption Line Region |
| BAM | Brewster Angle Microscopy |
| BAMEX | Bow Echo And MCV Experiment |
| BAMGAR | Barium Magnesium Germanate Garnet |
| BAN | British Approved Name (for Drugs) |
| BANSHEE | Beam Accelerator For Novel Super High Energy Electron |
| BAO | Best Atomic Orbital Basis |
| BAP | Bioavailable Phosphorus |
| BAPMON | Background Air Pollution Monitoring Network |
| BAQ | Building Air Quality |
| BARC | Bhabha Atomic Research Center |
| BARC | Bottom Antireflective Coating |
| BARF | Best Available Retrofit Facility |
| BARITT | Barrier Injection Transient Time |
| BART | Best Available Retrofit Technology |
| BART | Biological Activity Reaction Test |
| BASF | Badische Anilin- Und Soda-Fabrik |
| BASHD | Band Selective Homonuclear Decoupling |
| BASTE | Bay Area Sewage Toxics Emissions |
| BASTM | Beam-assisted Scanning Tunneling Microscope |
| BAT | Back Arc Tectonics |
| BAT | Best Available Technology |
| BAT | Biol. Tolerance Value (German Std.) |
| BAT | Brown Adipose Tissue |
| BATEA | Best Available Technology Economically Achievable |
| BATHEN | Burnable Fuel Abatement Through Efficient Improvement And Nonfossil Fraction Increase |
| BATNEEC | Best Available Technology Not Entailing Excessive Cost |
| BATS | Biosphere-Atmosphere Transfer Scheme |
| BATSE | Burst And Transient Source Experiment |
| BAW | Bond-order Alternation Wave (mol. Orbital) |
| BAW | Bulk Acoustic Wave |
| BAZ | Best Atom Zeta Basis Set |
| BAZ | Biologically Active Zones |
| BBB | Blood-brain Barrier |
| BBFM | Bond-bending Force Model (for Phonon Calcns.) |
| BBGKY | Bogoliubov-Born-Green-Kirkwood-Yvon Equations (in Kinetic Theory Of Fluids) |
| BBIC | Bioluminescent Bioreporter Integrated Circuits |
| BBK | Brauner-Briggs-Klar (wave Function In Atom-electron Scattering) |
| BBMV | Brush-border Membrane Vesicle |
| BBN | Big Bang Nucleosynthesis |
| BBO | Beta-barium Borate |
| BBO | Bonding Bond Orbital |
| BBP | Benzyl Butyl Phthalate |