| Acronym | Meaning |
| BLAISE | British Library Automated Information Service |
| BLAST | Basic Local Alignment Search Tool |
| BLAST | Burst Locations With Arc Second Telescope |
| BLB | Brillouin-Levy-Berthier (theorem In MO Theory) |
| BLC | B Lymphocyte Chemoattractant |
| BLC | BACT/LAER Clearinghouse |
| BLC | Borderless Contact |
| BLCAO | Bilinear Combination Of Atomic Orbitals |
| BLDSC | British Library Document Supply Centre |
| BLE | Bombardment-induced Light Emission |
| BLEVE | Boiling Liquid Expanding Vapor Explosion |
| BLIP | Background-limited Infrared Photodetector |
| BLIS | BACT/LAER Information System |
| BLISS | Balloon-borne Laser In Situ Sensor |
| BLM | Bureau Of Land Management |
| BLM | Bilayer Lipid Membrane |
| BLMO | Best Limited Basis Molecular Orbital |
| BLMO | Boys Localized Molecular Orbital |
| BLNK | B Cell Linker Protein |
| BLP | Bragg Light Profile |
| BLR | Broad Line Region |
| BLRG | Broad-line Radio Galaxy |
| BLS | Brillouin Light Scattering |
| BLS | Bureau Of Labor Statistics |
| BLS | Bare Lymphocyte Syndrome |
| BLT | Bismuth Lanthanum Titanate |
| BLTM | Branched Lagrangian Transport [model] |
| BLV | Bovine Leukemia Virus |
| BMA | British Medical Association |
| BMA | Butyl Methacrylate |
| BMAP | Biological Monitoring And Abatement Program |
| BMAS | Barium Magnesium Aluminosilicate |
| BMAW | Bare Metal Arc Welding |
| BMC | Benchmark Concentration |
| BMC | Bone Marrow Cell |
| BMC | Bone Mineral Content |
| BMC | Bulk-molding Compound |
| BMCD | Biological Macromolecule Crystallization Database |
| BMD | Born-Mayer (plus) Dispersion (potential Function) |
| BMD | Benchmark Dose |
| BMD | Bone Mineral Density |
| BMDL | Below Method Detection Level |
| BMDO | Ballistic Missile Defense Organization |
| BMEP | Brake Mean Effective Pressure |
| BMERC | BioMolecular Engineering Research Center |
| BMG | Bulk Metallic Glass |
| BMI | Body Mass Index |
| BMMO | Best Minimal Molecular Orbital |
| BMP | Best Management Practices |
| BMP | Biochemical Methane Potential |