| Major Research Instrumentation | Academic & Science |
| Mental Research Institute | Academic & Science |
| Meteorological Research Institute | Academic & Science |
| Magnetorotational Instability | Academic & Science |
| Midwest Research Institute | Academic & Science |
| Microwave Research Institute | Academic & Science |
| Mountain Research Initiative | Academic & Science |
| Monomial Representation Idempotent | Academic & Science |
| Medical Records Institute | Academic & Science |
| Anchorage (ak) | Airport Code |
| Maritime Rescue Institute | Associations & Organizations |
| Monthly Revenue Income. | Business |
| Management Recruiters International | Business |
| Macon Resources Inc | Business |
| Matz’s Ruby Interpreter | Computing |
| Monitor Line for Rings | Computing |
| Machine Readable Information | Computing |
| Magnetic Resonance Imaging | Electronic Device |
| Magnetic Resonance Imagery | Electronics |
| Mothers Rule Incorporated | General |
| Magnetic Resource Imaging | General |
| Method Replacement Indicator | General |
| Meuse Rhine Issel | General |
| My Ridiculous Insides | General |
| Myst Risk Indicator | General |
| Meaningless Repairable Injury | General |
| Magnetic Resonance Imaginging | General |
| Magnetic Resonance Imagining | General |
| Money Rolling In | General |
| Magnetic Resonance Iowa | General |
| Magnetic Reasonance Imaging | General |
| Mean Roughness Index | General |
| Maintenance Renewal Interval | General |
| Maxindo Renault Indonesia | General |
| Member of Royal Institution | General |
| Military Related Intelligence | Governmental |
| Mathematical Research Institute | Governmental |
| Meals, Ready to eat, Individual | Governmental |
| Monetary Research Institute | Governmental |
| Ministry of Research and Innovation | Governmental |
| Manufacturing Resources International | International |
| Medical Research Institute | Medical |
| Magnetic Resonate Imaging | Medical |
| Medical Reengineering Initiative | Medical |
| MILSTRIP Routing Indicator | Medical |
| Medical Resonance Imaging | Medical |
| Manchester Royal Infirmary | Medical |
| Monoamine Reuptake Inhibitor | Medical |
| Mohall Railroad | Regional |
| Measurement Requirements and Interface | Space Science |
| Moderate Resolution Imager | Space Science |
| Merrill Field | Transport & Travel |