| Abbreviation | Definition |
|---|---|
| MRCS | Machinery Repairman Senior Chief Petty Officer |
| MRFA | chinery Repairman Fireman Apprentice |
| MRFA | Machinery Repairman Fireman Apprentice |
| MRFN | chinery Repairman Fireman |
| MRFN | Machinery Repairman Fireman |
| MRFR | chinery Repairman Fireman Recruit |
| MRFR | Machinery Repairman Fireman Recruit |
| MS1 | Mess Attendant Specialist Petty Officer First Class |
| MS1 | ss Attendant Specialist Petty Officer First Class |
| MS2 | Mess Attendant Specialist Petty Officer Second Class |
| MS2 | ss Attendant Specialist Petty Officer Second Class |
| MS3 | Mess Attendant Specialist Petty Officer Third Class |
| MS3 | Mess Attendant Specialist Petty Officer Third Class |
| MSC | Mess Attendant Specialist Chief Petty Officer First Class |
| MSC | Mess Attendant Specialist Chief Petty Officer First Class |
| MSCM | Mess Attendant Specialist Master Chief Petty Officer |
| MSCM | ss Attendant Specialist Master Chief Petty Officer |
| MSCS | Mess Attendant Specialist Senior Chief Petty Officer |
| MSCS | ss Attendant Specialist Senior Chief Petty Officer |
| MSR | Metalsmith (ship Repair) |