| Abbreviation | Definition |
|---|---|
| MCPL | Mid Continent Public Library |
| MCPL | Middle Country Public Library |
| MCPL | Monroe County Public Library |
| MCPL | Montgomery County Public Libraries |
| MCPL | Montgomery County Public Library |
| MCPL | Morgan County Public Library |
| MDAL | Mesh Data Abstraction Library |
| MDL | Maryland Digital Library |
| MDL | MicroStation Development Libraries |
| MDLC | Minnesota Digital Library Coalition |
| MDLS | Member Digital Library Subscription |
| MDML | MOtOLOiD DANCE MUSIC LIBRARY |
| MEAA | Minerals Exploration Action Agenda |
| MedDRA | MedDRA Medical Dictionary for Regulatory Activities |
| MedDRA | Medical Dictionary for Regulatory Activities |
| MEDLARS | Medical Literature Analysis and Retrieval System |
| MEDLARS | Medical Literature Analysis and Retrieval System (NLM) |
| MedLav | Medicina del Lavoro (Industrial Medicine) (Milan) |
| MedPr | Medycyna Pracy (Medical Practice) (Warsaw) |
| MELA | Middle East Librarians Association |