| Abbreviation | Definition |
|---|---|
| BIU | Bus Interface Unit |
| BIW | Bath Iron Works |
| BK | Black Knights |
| BK | British Knights |
| BKA | BundesKriminalAmt (Federal Criminal Office) |
| BL | Base Level |
| BL | Basic Load |
| BL | BCXXI Lightweight Computer Unit |
| BL | Billeting Load |
| BL | Biocontainment Level |
| BL | Blast Link |
| BLA | Baloch Liberation Army |
| BLA | Baluchistan Liberation Army |
| BLA | Brigade Logistic Area |
| BLADE | Ballistic Low-Altitude Drone Engagement |
| BLCP | Beach Lighterage Control Point |
| BLD | Baseline Design |
| BLD | Billet Level Detail |
| BLDREP | BLooD REPort |
| BLDSHIPREP | BLooD SHIPment REPort |