| Abbreviation | Definition |
|---|---|
| OPAL | Opal Technologies, Inc. |
| OPAY | Official Payments Corporation |
| OPHD | Ophidian Pharmaceuticals |
| OPHDW | Ophidian Pharmaceuticals Warrants |
| OPHDW | Ophidian Pharmaceuticals Warrants (de-listed) |
| OPHDW | Ophidian Pharmaceuticals Warrants (de-listed) |
| OPHM | Orapharma |
| OPIX | Odyssey Pictures Corporation |
| OPKCE | Optika Investment Company |
| OPMC | Optimumcare Corporation |
| OPMK | Optimark Data Systems, Inc. |
| OPMNF | Opus Minerals, Inc. |
| OPMR | Optimal Robotics, Inc. |
| OPMX | Optimax Industries, Inc. |
| OPOF | Old Point Financial Corporation |
| OPSI | Optical Sensors, Inc. |
| OPST | O P T Sciences Corporation |
| OPSW | Opsware, Inc. |
| OPSY | Optical Systems, Inc. |
| OPTC | Optelecom, Inc. |