| Abbreviation | Definition |
|---|---|
| ONI | Office of Navy Intelligence |
| ONM | Ohio Naval Militia |
| ONR | Office of Naval Research's |
| OS | dinary Seaman |
| OS1 | erations Specialist Petty Officer 1st Class |
| OS1 | fficer's Steward 1st Class (non Petty Officer) |
| OS1 | Officer's Steward 1st Class (non Petty Officer) |
| OS1 | Operations Specialist Petty Officer 1st Class |
| OS2 | dinary Seaman 2nd Class |
| OS2 | erations Specialist Petty Officer 2nd Class |
| OS2 | fficer's Steward 2nd Class (non Petty Officer |
| OS2 | Officer's Steward 2nd Class (non Petty Officer |
| OS2 | Operations Specialist Petty Officer 2nd Class |
| OS2 | Ordinary Seaman 2nd Class |
| OS3 | erations Specialist Petty Officer 3rd Class |
| OS3 | fficer's Steward 3rd Class (non Petty Officer) |
| OS3 | Officer's Steward 3rd Class (non Petty Officer) |
| OS3 | Operations Specialist Petty Officer 3rd Class |
| OSC | erations Specialist Chief Petty Officer |
| OSC | Operations Specialist Chief Petty Officer |