List of acronyms: O

(Main list of acronyms)

O – Oberst – Observer – Obstacle – Octal – Officer – Official – Oh – Operational – Operator – Oprah (magazine) – Outstanding – Oxygen

OA

OA – Operational Analysis – Overeaters Anonymous
OAC – On Approved Credit
OAP – Old Age Pensioner
OAS – Organization of American States
OARSI – Osteoarthritis Research Society International
OASIS – Objects and Agents for Information Systems and Simulation – Organization for the Advancement of Structured Information Standards
OASIS – Ontario Agencies Supporting Individuals with Special Needs
OASIS – Ontario Association of Sewage Industry Services
OASP – Operational Analysis Support Paper/Plan
OAU – Organization of African Unity

OB

ob – obiit
OB
* Obedience
* Obligation
* Obligatory
* Obsolete
* Obstetrics
* Ocean Beach
* Off Break
* Old Bryanstonian
* Order of Battle
* Out-of-Bounds
* Outlet Box
* Overbought
* Oversight Board
OBE – Officer of the Order of the British Empire
OBJ
* Objective
* Odell Beckham Jr.
OBM – Obsidian Black Metallic
OBOR – One Belt One Road, a former name of the China-sponsored Belt and Road Initiative
OBS
* Observation/Observer
* Obsolete
* Obstacle
* Off Balance Sheet
* Optical Burst Switching
* Organic Brain Syndrome
* Organization(al) Breakdown Structure
OBSS
* Off Board Sensor Systems
* Ordo Byantinus Sancti Sepulchri
* Orbiter Boom Sensor System
* Origins Billion Star Survey
OBX – Outer Banks

OC

oc – Occitan language
OC – Officer Commanding
OCA – Observatoire de la Côte d'Azur – Offensive Counter-Air
OCD – Obsessive-Compulsive Disorder
OCFS – Oracle Cluster File System
OCFS – Office of Children & Family Services
OCFS2 – Oracle Cluster File System Release 2
oci – Occitan language
OCIDS – Optical Combat Identification System
OCMCC – Orchard County MCC
OCONUS - Outside Continental United States
OCN – Oncology Certified Nurse
OCO – Oort Cloud Object
OCOKA – Observation, Cover and concealment, Obstacles, Key terrain, and Avenues of approach
OCR – Optical Character Recognition
OCS – ''see entry''

OD

OE

OEA – Office of Economic Adjustment
OED – Oxford English Dictionary
OECD – Organisation for Economic Co-operation and Development
OEG – Operation Exposure Guidance
OEIS - On-Line Encyclopedia of Integer Sequences
OEM – Original equipment manufacturer

OF

OFA – Occipital Face Area
OFDA – 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 – Open Geospatial Consortium
OGD – Other Government Department
OGO – Other Government Organization
OGX – OUARGLA – a petroleum state in the south of Algeria

OH

OH – Ohio
OHC – OverHead-Cam engine
OHHLA – Original Hip-Hop Lyrics Archive
OHIP – Ontario Health Insurance Plan
OHMS – On His (or Her Majesty's Service)
OHP – Observatoire de Haute-Provence
OHSS – Ovarian Hyperstimulation Syndrome

OI

OIC – Officer In Charge
OIE – World Organisation for Animal Health
OIF – Operation Iraqi Freedom
OIOC – Oriental & India Office Collections

OJ

OK

OK
* Oklahoma
* oll korrect
OKC – Oklahoma City

OL

OLED – Organic Light-Emitting Diode
OLS – Operational Linescan System

OM

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

ON

ON – Ontario
Onna – Oniong, Nnung Ndem, and Awa, a Local Government Area in Nigeria
ONC – Orthopaedic Nurse Certified
ONCE – Organización Nacional de Ciegos Españoles
ONÉRA –
ONG – Orthodontic National Group
ONH – Óglaigh na hÉireann, used for the following:

Historically, as the Irish-language name for the original Irish Republican Army
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 – Office of Naval Intelligence
ONS – Operational Needs Statement

OO

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

OP

OP
* Observation Point/Post
* Ocean Pacific
* Original Poster
* Order Point, in inventory management; the inventory state at which more items should be ordered. Often expressed as a part of OP/OQ
* Overpowered, often used to refer to fictional characters or game mechanics that are considered disproportionately strong
OPA – Other Procurement, Army
OPAC – Online Public Access Catalogue
op cit – opera citata
OPCON – Operational control
OPCW – Organisation for the Prohibition of Chemical Weapons
OPEC – Organization of the Petroleum Exporting Countries
OpenStreetMap -
OPFOR – Opposing force
OPI
* Office of Primary Interest
* Open Prepress Interface
OPINTEL – Operational Intelligence
OPLAN – Operation plan
OPORD – Operation order
OPP
* Ontario Provincial Police
* Operational Planning Process
* Other People's Property/Pussy/Penis
OPS
* On-base plus slugging
* Operations
OPSEC
* Operations security
* Open Platform for Security
OPSI
* Overwhelming post splenectomy infection
* UK Office of Public Sector Information
OPTAR – Operational target
OPV – Offshore Patrol Vessel

OQ

OQ - Order Quantity, in inventory management; the quantity of new items to be ordered. Often expressed as a part of OP/OQ

OR

or – Oriya language
OR – Operating Room – Operational/Operations Research – Oregon - overreciprocation - when the leader of an inner circle friendship contacts a friend more than is wanted or reasonable
ORAU – Oak Ridge Associated Universities
ORB – Object Request Broker
ORBAT – Order of Battle
ORD – O'Hare International Airport in Chicago, Illinois
ORD – Office of Research and Development – Operational Requirements Document
ORF – Operational Readiness Float
ori – Oriya language
ORISE – Oak Ridge Institute for Science and Education
orm – Oromo language
ORNL – Oak Ridge National Laboratory
ORR – Oak Ridge Reservation – Office of Rail Regulation – Office of Refugee Resettlement – Office of Research and Reports – Operational Readiness Rate – Operational Readiness Review
ORSA – Oxacillin-resistant Staphylococcus aureus – Operations Research Society of America

OS

OS – Operating system
os – Ossetic language
Os – Osmium
OSA – Order of St. Augustine
OSCE – Organization for Security and Co-operation in Europe
OSD – U.S. Office of the Secretary of Defense – On-screen Display
OSDL – Open Source Development Labs
OSE – Own Separate Entrance
OSERS – U.S. Department of Education
OSETI – SETI also Optical SETI
OSGeo -
OSHA – Occupational Safety and Health Administration
OSI – Office of Strategic Influence – Ontario Swine Improvement – Open Source Initiative – Open Systems Interconnection
OSIA – On-Site Inspection Agency
OSL – Open Source License – Optically Stimulated Luminescence – Orbiting Solar Laboratory
OSIRIS
* Optical, Spectroscopic, and Infrared Remote Imaging System
* Optical System for Imaging and low Resolution Integrated Spectroscopy
OSM – One Saturday Morning
OSMF -
OSPA – Operations Security Professional's Association
OSPA – Oregon School Psychologists Association
OSRH – Oružane Snage Republike Hrvatske
oss – Ossetic language
OSS – Office of Strategic Services
OSU – Ohio State University – Oklahoma State University

OT

OTA – Occupational Therapy Assistant, Office of Technology Assessment – Orthodontic Technicians Association
OTAC – Orthodontic Technicians Association Conference – Orthodontic Technicians Association Council
OTB – Off The Ball – Offtrack Betting – OneSAF Testbed
OTC – Over-The-Counter
OTD – Off the derech
OTEA – Operational Test Evaluation Agency
OTI – Office of Transition Initiatives
*OTK One Turn Kill
OTO – Ordo Templi Orientis
OTOH – On The Other Hand
OTS – Off the scale, sexually untouchable except for a lot of money.
OTSBH – Over The Shoulder Boulder Holder
OTW – On The Way
OTYBL – Over To You Blue Leader
OTYRL – Over To You Red Leader

OU

OU – University of Oklahoma

OV

OVC
* Overcast
* Ohio Valley Conference
OVV – Optically Visually Violent, or Optically Violently Variable – a type of quasar

OW

OW – Old Wykehamist
OWN – Oprah Winfrey Network

OX

OX – IATA code for Orient Thai Airlines
OXC – Optical cross-connect
OXF – IATA code for London Oxford Airport
Oxfam – Oxford Committee for Famine Relief
OXM – Official Xbox Magazine
OXR – IATA code for Oxnard Airport
OXT – Oxytocin

OY

Oy – Osakeyhtiö
Oyj – ''Julkinen osakeyhtiö''

OZ

OZ – Ounce