| Abbreviation | Definition |
|---|---|
| OPRA | Options Price Reporting Authority |
| OPRA | Options Reporting Authority |
| OPRA | ptions Reporting Authority |
| OPS | Other Permanent Shareholders |
| OPSI | Office for Professional Standards and Integrity |
| OS | Open Street |
| OSE | Osaka Securities Exchange |
| OSE | Oslo Stock Exchange |
| OSE | saka Securities Exchange |
| OSE | slo Stock Exchange |
| OSF | Osaka Stock Futures 50 |
| OSO | Outperform Stock Options |
| OSS | Other Stable Shareholders |
| OSTI | Open Standard Trading Interface |
| OSX | Philadelphia Stock Exchange Oil Service Sector |
| OT | Orphan Trader |
| OTB | Open To Buy |
| OTC | Optical Telephone Corporation |
| OTCBB | Over The Counter Bulletin Board |
| OTCEI | Over the Counter Exchange of India |