HomePolice Jargon: O - Oscar
- OCD
- Officer in Charge of Division
- OIC
- Officer in Case
- Operation Tarian
- Operation supported by Home Office and the Welsh Assembly Government, drawing together the three south Wales forces to stem the flow of class A drugs into the area.
- Ops Room
- Operations Room at Headquarters (Also known as Force Control Room)
- OS
- Ordnance Survey
- OSPRE
- Name given to examination sat by Police Constables and Sergeants to attain qualification for promotion to the next rank.