| Abbreviation | Definition |
|---|---|
| MCEU | Massachusetts Central Railroad |
| MCEU | Massachusetts Central Railroad Corporation |
| MCEZ | Massachusetts Central Railroad |
| MCEZ | Massachusetts Central Railroad Corporation |
| MCHX | Monsanto Chemical Co. (Trinity Rail Management) |
| MCHX | Trinity Rail Management Incorporated |
| MCIX | Mobley Applied Chemicals Division |
| MCIX | SSI Mobley Company Incorporated (M of W) |
| MCKU | Mc Kinney Containers |
| MCLR | McLaughlin Line Railroad |
| MCLX | Morrison Car Leasing |
| MCMU | Management Control and Maintenance |
| MCMU | Management Control and Maintenance, S. A. |
| MCMX | M C Rail Services |
| MCPU | MCC Transport Singapore Pte Ltd. |
| MCPX | Monsanto |
| MCPX | Solutia Incorporated |
| MCR | McCloud Railway Company |
| MCR | McCloud River Railroad (McCloud Railway) |
| MCRR | Michigan Central Rail Road Line |