| Abbreviation | Definition |
|---|---|
| MRC | Minuteman Racing Club |
| MRD | Manitou Racing Development |
| MRD | Millennium Racing Development |
| MRE | Murdoch Racing Enterprises |
| MRH | Mikes Racing Heads |
| MRN | Major Races Number |
| MRN | Motor Racing Network |
| MRO | Motor Racing Outreach |
| MRP | Maui Raceway Park |
| MRRF | Motorcycle Road Racing Forums |
| MRRS | Marlboro Red Racing School |
| MRT | Mclelland's Racing Team |
| MRT | Mustang Racing Technologies |
| MRTE | Mini Racing Team Essonne |
| MRTU | Mini Racing Team Uden |
| MRW | MiniRaceWays Slot Car Speedway |
| MRW | Mizonokuchi Race Way |
| MSR | Manomet Street Racer |
| MSR | motor sports racing |
| MSRA | Maryland Street Racing Association |