(Main list of acronyms) O – (i) Oberst – Observer – Obstacle – Octal – Officer – Official – Oh – Operational – Operator – Oprah (magazine) – Outstanding – (s) Oxygen OA OA – (i) Operational Analysis – (i) Overeaters Anonymous OAC – (i) On Approved Credit OAP – Old Age Pensioner (UK) OAS – (i) Organization of American States OARSI – (i) Osteoarthritis Research Society International OASIS – (a) Objects and Agents for Information Systems and Simulation – Organization for the Advancement of Structured Information Standards OASIS – (a) Ontario Agencies Supporting Individuals with Special Needs OASIS – (a) Ontario Association of Sewage Industry Services OASP – (i) Operational Analysis Support Paper/Plan OAU – (i) Organization for African Unity OB ob – (p) obiit (Latin, "(s) he died") OB (p) Obedience Obligation Obligatory Obsolete Obstetrics (i) Ocean Beach (California) Off Break (cricket) Old Bryanstonian Order of Battle Outlet Box (electrical) (p) Overbought (stock market) (i) Oversight Board OBE – (i) Officer of the Order of the British Empire OBJ (p) Objective (military parlance) (i) Odell Beckham Jr. (American football wide receiver) OBM – (p) Obsidian Black Metallic (automobile paint color) OBOR – (i) One Belt One Road, a former name of the China-sponsored Belt and Road Initiative OBS (p) Observation/Observer Obsolete Obstacle (i) Off Balance Sheet Optical Burst Switching (IEEE) Organic Brain Syndrome Organization(al) Breakdown Structure OBSS (i) Off Board Sensor Systems Ordo Byantinus Sancti Sepulchri (Byzantine Order of the Holy Sepulchre) Orbiter Boom Sensor System (space shuttle) Origins Billion Star Survey OBX – (p) Outer Banks (North Carolina) OC oc – (s) Occitan language (ISO 639-1 code) OC – (i) Officer Commanding OCA – (i) Observatoire de la Côte d'Azur – Offensive Counter-Air OCD – (i) Obsessive-Compulsive Disorder OCFS – (i) Oracle Cluster File System OCFS – (i) Office of Children & Family Services OCFS2 – (i) Oracle Cluster File System Release 2 oci – (s) Occitan language (ISO 639-2 code) OCIDS – (i) Optical Combat Identification System OCMCC – (i) Orchard County MCC OCONUS Outside Continental United States OCN – (i) Oncology Certified Nurse OCO – (i) Oort Cloud Object OCOKA – (a) Observation, Cover and concealment, Obstacles, Key terrain, and Avenues of approach (mnemonic) OCR – (i) Optical Character Recognition OCS – see entry OD OD (i) Old Dragon Ordnance Datum (nautical charts) (p) Overdose ODAS – (a) OCA-DLR Asteroid Survey ODB (i) Ol' Dirty