| Abbreviation | Definition |
|---|---|
| MOV | Motorcar Operators West railroad motorcars |
| MOW | Maintenance Of Way |
| MOW | Motorcar Operators West railroad motorcars |
| MOWX | Fortaleza Construction |
| MOXV | Moxahala Valley Railway |
| MP | Missouri Pacific Railroad (Union Pacific Railroad) |
| MP | Union Pacific Railroad Company |
| MPA | Maryland and Pennsylvania Railroad |
| MPA | Maryland and Pennsylvania Railroad (York Railway) |
| MPCX | Michels Pipeline Construction Incorporated |
| MPCX | Moyer Packing (Michels Pipeline Construction) |
| MPEX | MotivePower Industries |
| MPEX | Motivepower Industries Incorporated |
| MPIT | Missouri Pacific Railroad (Union Pacific Railroad) |
| MPIT | Union Pacific Railroad Company |
| MPIU | MEMC Pasadena |
| MPIX | Motive Power Incorporated |
| MPIX | Myer's Propane Gas Service (Motive Power) |
| MPLI | Minnesota Prairie Line |
| MPLX | GE Rail Services |