| Abbreviation | Definition |
|---|---|
| MELO | Mississippi Electronic Libraries Online |
| MELP | Mamie Eisenhower Library Project |
| MENALIB | Middle East / North Africa Virtual LIBrary |
| MeSH | medical subject headings |
| METS | Metadata Encoding and Transmission Standard |
| MFL | MAT File Library |
| MFL | Monroe Free Library |
| MFPL | Mansfield Free Public Library |
| MFPL | Martins Ferry Public Library |
| MFPL | Mattapoisett Free Public Library |
| MFPL | Menomonee Falls Public Library |
| MFPL | Millburn Free Public Library, Millburn, New Jersey |
| MFPL | Milton-Freewater Public Library |
| MFRL | Montgomery Floyd Regional Library |
| MFS | MicroFilm Systems, Colorado Springs, Colorado Library code |
| MGCL | Mahatma Gandhi Central Library |
| MGPL | Merriam-Gilbert Public Library |
| MGPL | Morton Grove Public Library |
| MHL | Medical Heritage Library |
| MHL | Medical Heritage Library (digital) |