| Abbreviation | Definition |
|---|---|
| MDI | Mule Deer Initiative |
| MDNA | Milwaukee District Nurses Association |
| MDPA | Mount Diablo Pilots Association |
| MDS | Mennonite Disaster Service |
| MDSC | Mood Disorders Society of Canada |
| MDSO | Miss Delaware Scholarship Organization |
| MEA | Marine Executive Association |
| MEA | Media Ecology Association |
| MEAC | Madisonville Education and Assistance Center |
| MEAL | Monitoring, Evaluation, Accountability and Learning |
| MEBTC | Midwest Eye-Banks and Transplantation Center |
| MEC | Michigan Environmental Council |
| MECC | Middle East Council of Churches |
| MEDA | Mission Economic Development Agency |
| MEDF | Minerva Education and Development Foundation |
| MEG | The Marketing Educator's Group |
| MEI | Medical Education Institute |
| MEII | Medical Education Institute, Inc. |
| MEII | Medical Education Institute, Incorporated |
| MEL | Measuring Evaluation Level |