| Abbreviation | Definition |
|---|---|
| MCRR | Michigan Central RailRoad |
| MCRR | Monongahela Connecting Railroad |
| MCRR | Monongahela Connecting RR Company |
| MCRT | Mass Central Rail Trail |
| MCRT | Massachusetts Central Rail Trail |
| MCRX | Marcus Corporation |
| MCRX | Marcus Rail Transport |
| MCRY | Mid Continent Railway |
| MCSA | Moscow Camden and San Augustine Railroad |
| MCSA | Moscow, Camden and San Augustine Railroad |
| MCSR | Modular Combat Suppressor Rail |
| MCSU | China Ocean Shipping |
| MCSU | China Ocean Shipping Company |
| MCTA | Minnesota Central Railroad |
| MCTA | Minnesota Central Railroad Company |
| MCTX | Modern Continental Construction |
| MCVX | Massachusetts Call Volunteer Firefighters' Association |
| MCVX | Massuchusetts Call/Volunteer Firefighters Association |
| MD | Municipal Docks |
| MDAX | Merchants Despatch Transportation Corporation |