| Abbreviation | Definition |
|---|---|
| ABR | Amateur Baseball Report |
| ABSA | African Baseball & Softball Association |
| ACBL | Atlantic Collegiate Baseball League |
| ACSB | Alamo City Select Baseball |
| AFBL | Advanced Fall Baseball League |
| AFBL | American Federation Baseball League |
| AIBC | Arizona International Baseball Consortium |
| AJB | Ambler Junior Baseball |
| AJB | Ambler Junior Baseball Ambler Junior Baseball |
| ALCSMVP | American League Championship Series Most Valuable Player |
| ALLB | Alvin Little League Baseball |
| ALPB | Atlantic League of Professional Baseball |
| ALWC | American League Wild Card |
| AMBL | Austin Metro Baseball League |
| APBA | American Professional Baseball Association |
| APBC | Asia Professional Baseball Championship |
| APW | Adjusted Pitcher Wins |
| ARI | Arizona Diamondbacks |
| ASB | All Star Baseball |
| ASB | Austin Select Baseball |