| Abbreviation | Definition |
|---|---|
| MR | Mister |
| MR | Modification Request |
| MRA | Multi Rater Assessment |
| MRA | Mutual Recognition Arrangement |
| MRC | Mississippi River Commission |
| MRF | Materials Recovery Facility |
| MRL | minimal risk level |
| MRO | Mooresville Regional Office |
| MRP | Managerial Reporting Program |
| MRR | Management Requirements Review |
| MRR | Materials Reclamation Or Recovery |
| MRSS | Marine Radio Safety Service |
| MRT | Management Review Team |
| MRU | Maximum Rule Use |
| MS | Mail Slot |
| MS | Major Supplier |
| MSA | Metropolitan Sampling Area |
| MSA | Metropolitan Statistical Area |
| MSA | Militaristic Secret Agency |
| MSA | Mine Safety Administration |