| Abbreviation | Definition |
|---|---|
| MABL | Mens Adult Baseball League |
| MABL | Metro Area Baseball League |
| MATB | Mid Atlantic Tournament Baseball |
| MBA | Mississauga Baseball Association |
| MBBL | Markham Business Baseball League |
| MBBL | McGuane Bridgeport Baseball League |
| MBBN | Mobile BayBears Baseball Network |
| MBCA | Massachusetts Baseball Coaches Association |
| MBGA | Make Baseball Great Again |
| MBI | Mesquite Baseball Inc |
| MBSA | Manalapan Baseball and Softball Association |
| MBSA | Mundelein Baseball and Softball Association |
| MBSL | Miamisburg Baseball and Softball League |
| MBT | Minnesota Baseball Tournaments |
| MCPB | McLean County PONY Baseball |
| MDBA | Markham District Baseball Association |
| MIA | Miami Marlins |
| MIL | Milwaukee Brewers |
| MiLB | Minor League Baseball |
| MLB | Major League Baseball |