| Abbreviation | Definition |
|---|---|
| OMK | One Man Klan |
| OML | Open Meeting Law |
| OND | Officer Next Door |
| OOB | Out On Bail |
| OOC | Out Of Control |
| OOJ | Order Of Justice |
| OP | Old Prison |
| OPA | Official Police Action |
| OPAA | Ohio Prosecuting Attorneys Association |
| OPD | Office of Public Defence |
| OPD | Ottawa Police Department |
| OPN | Opinion |
| OPP | Other Peoples Property |
| OPPA | Ontario Political Payoff Act |
| OPUS | Offender Population United System |
| OQE | Objective Quality Evidence |
| OSB | Oregon State Bar |
| OSC | Office of State Controller |
| OSC | Organized Serial Crimes |
| OSM | Officially Slightly Mad |