# List of acronyms: O

This list contains acronyms, initialisms, and pseudo-blends that begin with the letter O.
For the purposes of this list:
* acronym = an abbreviation pronounced as if it were a word, e.g., SARS = severe acute respiratory syndrome, pronounced to rhyme with cars
* initialism = an abbreviation pronounced wholly or partly using the names of its constituent letters, e.g., CD = compact disc, pronounced cee dee
* pseudo-blend = an abbreviation whose extra or omitted letters mean that it cannot stand as a true acronym, initialism, or portmanteau (a word formed by combining two or more words).
    (a) = acronym, e.g.: SARS – (a) severe acute respiratory syndrome
    (i) = initialism, e.g.: CD – (i) compact disc
    (p) = pseudo-blend, e.g.: UNIFEM – (p) United Nations Development Fund for Women
    (s) = symbol (none of the above, representing and pronounced as something else; for example: MHz – megahertz)
Some terms are spoken as either acronym or initialism, e.g., VoIP, pronounced both as voyp and V-O-I-P.
(Main list of acronyms)

## Contents

* Top
* O0–9 OA OB OC OD OE OF OG OH OI OJ OK OL OM ON OO OP OQ OR OS OT OU OV OW OX OY OZ
* 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:
* Historically, as the Irish-language name for the original Irish Republican Army ("Old IRA")
* In modern times, as the Irish-language name of the Defence Forces of Ireland
* 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)
** OTK One Turn Kill
* 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