List of acronyms: O

(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 Bastard (rapper)
 * (i) One Dirty B*tch/Broad/Babe (professional wrestler)
 * (i) Operational Data Base
 * (i) Original David Baker (professional poker player; used to distinguish from another professional poker player of the same name)
 * (i) Oxford Dictionary of Byzantium
 * ODBC – (i) Open DataBase Connectivity
 * ODI
 * (i) Office for Disability Issues (UK government agency)
 * One Day International (cricket)
 * Open Data-Link Interface
 * Oracle Data Integrator
 * Overseas Development Institute (UK think tank)

OE

 * OEA – (i) (U.S.) Office of Economic Adjustment
 * OED – (i) Oxford English Dictionary
 * OECD – (i) Organisation for Economic Co-operation and Development (international)
 * OEG – (i) Operation Exposure Guidance
 * OEIS - (i) On-Line Encyclopedia of Integer Sequences
 * OEM – (i) Original Equipment Manufacturer

OF

 * OFA – (i) Occipital Face Area
 * OFDA – (i) U.S Agency for International Development's Office of Foreign Disaster Assistance

OG

 * OG:
 * Objective Glass, see Objective (optics)
 * Obstetrics and gynaecology
 * Offensive Guard, see Guard (American football)
 * Old Giggleswickian, a former pupil of Giggleswick School
 * Old Gower, a former pupil of University College School
 * Old Gregorian, a former pupil of Downside School
 * Old Greshamian, a former pupil of Gresham's School
 * Old Gold, a dark yellow
 * Olympic Games
 * Original Gangster, see Gangster
 * Original Gravity, see Gravity (beer)
 * Outpost Gallifrey, a Doctor Who fansite.
 * Own goal, in soccer, a goal scored by a player in their own side's goal
 * OG: Optimized Gaia, theory the earth optimizes itself to promote life, and popular movement to Promote Human Progress in Harmony with the Natural World.
 * OG: Original Gangster, an album by Ice-T
 * OGC – (i) Open Geospatial Consortium
 * OGD – (i) Other Government Department
 * OGO – (i) Other Government Organization
 * OGX – OUARGLA – a petroleum state in the south of Algeria

OH

 * OH – (s) Ohio (postal symbol)
 * OHC – (i) OverHead-Cam engine
 * OHHLA – (a) Original Hip-Hop Lyrics Archive
 * OHIP – (a) Ontario Health Insurance Plan
 * OHMS – (i) On His (or Her Majesty's Service) (also written: O.H.M.S.)
 * OHP – (i) Observatoire de Haute-Provence
 * OHSS – (p) Ovarian Hyperstimulation Syndrome

OI

 * OIC – (i) Officer In Charge
 * OIE – (i) World Organisation for Animal Health (originally the Office international des épizooties, French for "International Epizootic Office")
 * OIF – (i) Operation Iraqi Freedom
 * OIOC – (i) Oriental & India Office Collections (in the British Library)

OJ

 * oj – (s) Anishinaabe language (Ojibwa) (ISO 639-1 code)
 * OJ – (i) Orange Juice – O. J. Simpson
 * oji – (s) Anishinaabe language (Ojibwa) (ISO 639-2 code)
 * OJT – On-the-Job Training

OK

 * OK
 * (s) Oklahoma (postal symbol)
 * (i) oll korrect (facetious alteration of "all correct", 1839)
 * OKC – (a) Oklahoma City

OL

 * OLED – (a) Organic Light-Emitting Diode
 * OLS – (i) Operational Linescan System

OM

 * om – (s) Oromo language (ISO 639-1 code)
 * OM – (s) Oman (ISO 3166 digram) – Olympique de Marseille (French football club)
 * OMA – (i) Open Mobile Alliance – Operations & Maintenance, Army
 * OMB – (i) U.S. Office of Management and Budget – Ontario Municipal Board – (i) Order of Mapungubwe in Bronze
 * OMD – (i) Orchestral Manoeuvres in the Dark (1980s pop group)
 * OME – (i) Osaka Mercantile Exchange
 * OMFG – (i) Oh My F**king God
 * OMG – (i) Oh My God or Or My Gosh
 * OMGW – (i) "Oh My Gosh it's Windy"
 * OMN – (s) Oman (ISO 3166 trigram)
 * OMNCS – (i) U.S. Office of the Manager for the National Communications System
 * OMP – (i) Order of Mapungubwe in Platinum
 * OMR – (s) Omani rial (ISO 4217 currency code)
 * OMS – (i) Order of Mapungubwe in Silver
 * OMT – (i) Object Model Template
 * OMW – (i) On My Way, Oh My Word

ON

 * ON – (s) Ontario (postal symbol)
 * Onna – Oniong, Nnung Ndem, and Awa, a Local Government Area in Nigeria
 * ONC – (i) Orthopaedic Nurse Certified
 * ONCE – (a) Organización Nacional de Ciegos Españoles (Spanish, "National Organization for the Spanish Blind")
 * ONÉRA – (a) Office national d'études et de recherches aérospatiales (French, "Aeronautics and Space Research Center")
 * ONG – (i) Orthodontic National Group
 * ONH – (i) Óglaigh na hÉireann (Irish idiom for "soldiers of Ireland"), used for the following:
 * 1) Historically, as the Irish-language name for the original Irish Republican Army ("Old IRA")
 * 2) In modern times, as the Irish-language name of the Defence Forces of Ireland
 * 3) The name of two groups claiming descent from the Old IRA, one a currently inactive splinter group of the Continuity IRA and the other an active splinter group of the Real IRA
 * ONI – (i) (U.S.) Office of Naval Intelligence
 * ONS – (i) Operational Needs Statement

OO

 * OO – (i) Object Oriented – Over & Out
 * OOO – (i) Out Of the Office
 * OOAD – (i) Object-Oriented Analysis and Design
 * OOBE – (a) Out-of-body experience
 * OOCL – (i) Orient Overseas Container Line
 * OODA – (i) Observation, Orientation, Decision, Action loop (a.k.a. Boyd's Loop)
 * OOMF – (i) One Of My Followers
 * OOP – (i) Object-Oriented Programming – Out Of Print
 * OOS – (i) Occupational Overuse Syndrome – OneSAF Objective System – Open Operating System – Out Of Service
 * OOTW – (i) (Military) Operations Other Than War (MOOTW or OOTW)

OP

 * OP
 * (i) Observation Point/Post
 * Ocean Pacific (surfwear and swimwear brand)
 * Original Poster (internet)
 * Order Point, in inventory management; the inventory state at which more items should be ordered. Often expressed as a part of OP/OQ (when quantity OP is reached, order OQ new items)
 * Overpowered, often used to refer to fictional characters (e.g. Superman) or game mechanics (e.g. the Black Lotus in Magic: the Gathering) that are considered disproportionately strong
 * OPA – (i) Other Procurement, Army
 * OPAC – (a) Online Public Access Catalogue
 * op cit – (p) opera citata (Latin, "in the work cited")
 * OPCON – (p) Operational control
 * OPCW – (i) Organisation for the Prohibition of Chemical Weapons
 * OPEC – (a) Organization of the Petroleum Exporting Countries


 * OpenStreetMap - (p) OpenStreetMap
 * OPFOR – (p) Opposing force(s)
 * OPI
 * (i) Office of Primary Interest
 * Open Prepress Interface
 * OPINTEL – (p) Operational Intelligence
 * OPLAN – (p) Operation plan (also OpPlan)
 * OPORD – (p) Operation order
 * OPP
 * (i) Ontario Provincial Police
 * Operational Planning Process
 * Other People's Property/Pussy/Penis (song)
 * OPS
 * (i) On-base plus slugging (baseball statistics)
 * (p) Operations
 * OPSEC
 * (p) Operations security
 * Open Platform for Security
 * OPSI
 * (a) Overwhelming post splenectomy infection
 * UK Office of Public Sector Information
 * OPTAR – (p) Operational target
 * OPV – (i) Offshore Patrol Vessel

OQ

 * OQ - (i) Order Quantity, in inventory management; the quantity of new items to be ordered. Often expressed as a part of OP/OQ (when quantity OP is reached, order OQ new items)

OR

 * or – (s) Oriya language (ISO 639-1 code)
 * OR – (i) Operating Room (surgery) – Operational/Operations Research – (s) Oregon (postal symbol) - overreciprocation - when the leader of an inner circle friendship contacts a friend more than is wanted or reasonable
 * ORAU – (a/i) Oak Ridge Associated Universities
 * ORB – (a/i) Object Request Broker
 * ORBAT – (p) Order of Battle
 * ORD – (i) O'Hare International Airport in Chicago, Illinois (IATA Airport Code ORD)
 * ORD – (i) Office of Research and Development – Operational Requirements Document
 * ORF – (i) Operational Readiness Float
 * ori – (s) Oriya language (ISO 639-2 code)
 * ORISE – (a) Oak Ridge Institute for Science and Education
 * orm – (s) Oromo language (ISO 639-2 code)
 * ORNL – (i) Oak Ridge National Laboratory
 * ORR – (i) Oak Ridge Reservation (U.S. DOE) – Office of Rail Regulation (UK government) – Office of Refugee Resettlement – (CIA) Office of Research and Reports – Operational Readiness Rate – Operational Readiness Review
 * ORSA – Oxacillin-resistant Staphylococcus aureus – Operations Research Society of America

OS

 * OS – (s) Operating System
 * os – (s) Ossetic language (ISO 639-1 code)
 * Os – (s) Osmium
 * OSA – (i) Order of St. Augustine
 * OSCE – (i) Organization for Security and Co-operation in Europe
 * OSD – (i) U.S. Office of the Secretary of Defense – (i) On-screen Display
 * OSDL – (i) Open Source Development Labs
 * OSE – (a) Own Separate Entrance
 * OSERS – (a) U.S. Department of Education Office of Special Education and Rehabilitative Services
 * OSETI – (a) Optical SETI also Optical SETI


 * OSGeo - (a) Open Source Geospatial Foundation (OSGeo)
 * OSHA – (a) Occupational Safety and Health Administration
 * OSI – (i) Office of Strategic Influence – Ontario Swine Improvement – Open Source Initiative – Open Systems Interconnection
 * OSIA – (i) (U.S.) On-Site Inspection Agency
 * OSL – (i) Open Source License – Optically Stimulated Luminescence – Orbiting Solar Laboratory
 * OSIRIS
 * (a) Optical, Spectroscopic, and Infrared Remote Imaging System (astronomical system on the Rosetta spacecraft)
 * Optical System for Imaging and low Resolution Integrated Spectroscopy (astronomical system on the land-based Gran Telescopio Canarias)
 * OSM – (i) One Saturday Morning
 * OSMF - (a) OpenStreetMap Foundation
 * OSPA – (a) Operations Security Professional's Association site of OSPA


 * OSPA – (i) Oregon School Psychologists Association
 * OSRH – (i) Oružane Snage Republike Hrvatske (en: Armed forces of the Republic of Croatia)
 * oss – (s) Ossetic language (ISO 639-2 code)
 * OSS – (i) Office of Strategic Services (1942–1945, forerunner of CIA)
 * OSU – (i) Ohio State University – Oklahoma State University

OT

 * OTA – Occupational Therapy Assistant, (i) Office of Technology Assessment – (a/i) Orthodontic Technicians Association
 * OTAC – (i) Orthodontic Technicians Association Conference – (i) Orthodontic Technicians Association Council
 * OTB – (i) Off The Ball – (i) Offtrack Betting – (p) OneSAF Testbed (a descendant of ModSAF)
 * OTC – (i) Over-The-Counter (drugs)
 * OTD – (i) Off the derech (referring to an Orthodox Jew who has stopped practicing the tenets of his or her faith)
 * OTEA – (i) (U.S. Army) Operational Test Evaluation Agency
 * OTI – (i) Office of Transition Initiatives (United States Agency for International Development)
 * OTO – (i) Ordo Templi Orientis (Latin, "Order of the Temple of the East", i.e. the Order of Oriental Templars)
 * OTOH – (i) On The Other Hand
 * OTS – Off the scale, sexually untouchable except for a lot of money.
 * OTSBH – (i) Over The Shoulder Boulder Holder
 * OTW – (i) On The Way
 * OTYBL – (i) Over To You Blue Leader
 * OTYRL – (i) Over To You Red Leader

OU

 * OU – (p) University of Oklahoma

OV

 * OVC
 * (s) Overcast (METAR Code)
 * (i) Ohio Valley Conference
 * OVV – (i) Optically Visually Violent, or Optically Violently Variable – a type of quasar

OW

 * OW – (i) Old Wykehamist
 * OWN – (i) Oprah Winfrey Network

OX

 * OX – (p) IATA code for Orient Thai Airlines
 * OXC – (p) Optical cross-connect
 * OXF – (p) IATA code for London Oxford Airport
 * Oxfam – (p) Oxford Committee for Famine Relief (international poverty relief organization)
 * OXM – (i) Official Xbox Magazine
 * OXR – (p) IATA code for Oxnard Airport
 * OXT – (s) Oxytocin

OY

 * Oy – (p) Osakeyhtiö (Finnish, "stock company")
 * Oyj – (p) Julkinen osakeyhtiö (Finnish, "public stock company")

OZ

 * OZ – Ounce