| Abbreviation | Definition |
|---|---|
| OHIPM | Ohio Power Company Class M (de-listed) |
| OHIPN | Ohio Power Company Class N |
| OHIPN | Ohio Power Company Class N (de-listed) |
| OHIPN | Ohio Power Company Class N (de-listed) |
| OHIPO | Ohio Power Company Class O |
| OHIPO | Ohio Power Company Class O (de-listed) |
| OHIPO | Ohio Power Company Class O (de-listed) |
| OHIPP | Ohio Power Company Class P |
| OHIPP | Ohio Power Company Class P (de-listed) |
| OHIPP | Ohio Power Company Class P (de-listed) |
| OHRI | Occupational Health and Rehabilitation, Inc. |
| OHSB | Ohio State Bankshares |
| OICO | O I Corporation |
| OILS | Synergy Technologies Corporation |
| OISI | Opthalmic Imaging Systems, Inc. |
| OJOC | Ojai Oil Company |
| OJSY | OJsys, Inc. |
| OKOK | Oklahoma Energy Corporation |
| OKRG | Oakridge Holdings, Inc. |
| OKSB | Southwest Bancorp, Inc., of Oklahoma |