| Abbreviation | Definition |
|---|---|
| MEL | Monitoring Evaluation Level |
| MEM | MEMber |
| MENC | Mensa of Eastern North Carolina |
| MEND | Mind, Exercise, Nutrition, Do It! |
| MERF | Mensa Education Research Foundation |
| MERG | Mainstem Eel River Group |
| MERIT | Membership Excellence Recruitment Initiative Team |
| MERP | Medication Errors Reporting Program |
| MESA | Mathematics Engineering Science Association |
| MESA | Medical Equipment and Supplies Abroad |
| MESA | Mens' Educational Support Association |
| MESA | Mesa Equine Sanctuary and Adoption |
| MESSAD | Mouvement pour l'Education, la SAnte et le Developpement |
| MEWA | Maine Equine Welfare Alliance |
| MF | MATHCOUNTS Foundation |
| MF | Membership Function |
| MFCG | Manx Footpath Conservation Group |
| MFCG | Mycosis Fungoides Cooperative Group |
| MFF | Milken Family Foundation |
| MFFK | Massachusetts Families For Kids |