| Abbreviation | Definition |
|---|---|
| MRRS | Metrowest Radio Reading Service |
| MRT | Männer organisieren Radikale Therapie |
| MRTA | Manitoba Recreational Trails Association |
| MS | Mercy Ships |
| MSA | Medcin Sans Atmosphere |
| MSAA | Multiple Sclerosis Association of America |
| MSC | Margaret Sanger Center |
| MSC | Monroe Senior Center |
| MSC | Moved, Seconded, and Carried |
| MSCC | Monroe Senior Citizens Center |
| MSCF | Main Street Community Foundation |
| MSCF | Mid-Shore Community Foundation |
| MSCH | Mountain States Children's Home |
| MSCI | Margaret Sanger Center International |
| MSCK | Medical Society of the County of Kings, Inc. |
| MSCV | Motorcycle Safety Center of Virginia |
| MSDA | Michigan Sleep Disorders Association |
| MSDA | Mississippi Sleep Disorders Association |
| MSDL | Mid-South Delta Leaders |
| MSEA | Mission Society of Enrolled Agents |