| Abbreviation | Definition |
|---|---|
| MDR | Major District Road |
| MDS | Material Distribution Services |
| MDS | Multi Displacement System |
| MDS | Multiple Dead Stick |
| MDT | Harrisburg International |
| MDT | Medium Duty Truck |
| MdTA | Maryland Toll Authority |
| MDTA | Miami Dade Transit Agency |
| MDTQ | Maximum Daily Transportation Quantity |
| MDV | Mars Descent Vehicle |
| MDV | Maximum Duty Vehicle |
| MDV | Medium Duty Vehicle |
| MDW | Chicago Midway Airport |
| MEA | Minimum En Route IFR Altitude |
| MEA | Minimum Enroute Altitude |
| MEBA | Marine Engineers Beneficial Association |
| MECH | Motor, Expander, Compressor, And Hydraulics |
| MECV | Modernized Expanded Capacity Vehicle |
| MED | Marine Equipment Directive |
| MEL | Maritime Economics and Logistics |