

| Acronym | Sense | Language | Topics | 
|---|---|---|---|
| OMPF | Official Military Personnel File | In English | → Personnel management → Military affairs | 
| OMPR | Operational Maintainability Problem Reporting | In English | → Maintenance and logistics | 
| OMPT | Observed Mass Point Trajectory | In English | |
| OMR | Optical Mark Recognition | In English | → Writing systems → Computer-based techniques | 
| OMR | Operations and Maintenance Requirement | In English | → Maintenance and logistics | 
| OMR | Operations Management Room | In English | → Management | 
| OMR | Orbiter Management Review | In English | → Management → Astronautics | 
| OMRB | Operating Material Review Board | In English | |
| OMRC | Operational Maintenance Requirements Catalog | In English | → Maintenance and logistics | 
| OMRF | Orbiter Maintenance and Refurbishment Facility | In English | → Maintenance and logistics → Astronautics | 
| OMRF | Orbiter Modification and Refurbishment Facility | In English | → Maintenance and logistics → Astronautics | 
| OMRP | Operations and Maintenance Requirements Plan | In English | → Maintenance and logistics | 
| OMRS | Operations and Maintenance Requirements and Specifications | In English | → Maintenance and logistics | 
| OMRS | Operations and Maintenance Requirements System | In English | → Maintenance and logistics | 
| OMRSCB | Operations and Maintenance Requirements and Control Board | In English | → Maintenance and logistics | 
| OMRSD | Operations and Maintenance Requirements and Specifications Document | In English | → Maintenance and logistics | 
| OMS | Orbital Maneuvering System | In English | → Astronautics | 
| OMS | Operations Management System | In English | → Management | 
| OMSP | Operational Maintenance Support Plan | In English | → Management | 
| OMSP | Open Market Selling Price | In English | → Prices | 
| OMT | Osteopathic Manipulative Treatment | In English | → Medicine | 
| OMT | Object-Modeling Technique | In English | → Software | 
| OMU | Optical Measuring Unit | In English | → Optics | 
| OMV | Orbital Maneuvering Vehicle | In English | → Astronautics | 
| OMV | Oxygen Manual Valve | In English | |
| OMVS | Optically Variable Magnetic Stripe | In English | → Optics | 
| ONAMA | Ontology of Narratives of the Middle Ages | In English | → Linguistics → History | 
| ONBT | Orbiter Neutral Buoyancy Trainer | In English | → Astronautics | 
| OND | Operator Need Date | In English | |
| ONE | Organisation Naturiste Européenne (www.onenaturism.com) | In English | → Organizations and associations | 
| ONGC | Oil and Natural Gas Corporation (www.ongcindia.com) | In English | → Earth sciences → Mining | 
| ONGC | Office des Normes Générales du Canada | In English | → Standardization → Canada | 
| ONR | Office of Naval Research | In English | → Military engineering | 
| ONRAS | Occasional Notes of the Royal Astronomical Society | In English | → Serial publications, periodicals → Astronomy | 
| ONT | Optical Network Terminal | In English | → Networks, communication → Telecommunications | 
| ONT | Ontario International Airport (https://www.flyontario.com) | In English | → Transport by air → Canada | 
| OntoUCP | Ontology based Unified Communication Protocol | In English | → Software → Networks, communication | 
| OntoUCP | Ontology-based Unified Communication Protocol | In English | → Programming languages | 
| OOD | Object-Oriented Design | In English | |
| OOD | Orbiter On Dock | In English | → Astronautics | 
| OODP | Out-Of-Detent Pitch | In English | |
| OODR | Out-Of-Detent Roll | In English | |
| OOH | Orbital Operations Handbook | In English | → Astronautics | 
| OOMM | Organizational Operations and Maintenance Manual | In English | → Maintenance and logistics | 
| OOP | Over Optimization Penalty | In English | |
| OOR | On-Orbit Review | In English | → Astronautics | 
| OOS | On-Orbit Station | In English | → Astronautics | 
| OOS | Orbit-to-Orbit Shuttle | In English | → Astronautics | 
| OOS | Orbit-to-Orbit Stage | In English | → Astronautics | 
| OOSD | On-Orbit Support Document | In English | → Astronautics | 
| OOSD | Orbital Operations Support Document | In English | → Astronautics | 
| OOSDP | On-Orbit Station Distribution Panel | In English | → Astronautics | 
| OOSS | On-Orbit Support System | In English | → Astronautics | 
| OP | Operating Procedure | In English | → Management | 
| OP | Optional Protocol = PF | Protocole Facultatif | In French | In English | → International law | 
| OP&R | Operations Planning and Requirements | In English | → Management | 
| OPA | Online Publishers Association (www.online-publishers.org) | In English | → Associations → Graphic industries, printing, publishing | 
| OPA | Operations Planning Analysis | In English | → Management | 
| OPA | Ontario Psychological Association (www.psych.on.ca) | In English | → Associations → Psychology → Canada | 
| OPA | Other Procurement, Army | In English | → Military affairs | 
| OPAC | Online Public Access Catalog | In English | → Libraries | 
| OPB | Oxidizer Preburner | In English | → Vehicle engineering | 
| OPBS | Orbiter Payload Bay Simulator | In English | → Astronautics | 
| OPC | Open Process Control | In English | → Data | 
| OPC | Optical Power Calibration | In English | → Optics | 
| OPC | Opel Performance Center | In English | → Automobile manufacturing | 
| OPC | OLE for Process Control | In English | → Networks, communication | 
| OPC | Oligodendrocy Precursor Cell | In English | → Cytology | 
| OPC | Organic Photo Conductor | In English | → Peripheral devices | 
| OPC | Orthodox Presbyterian Church (www.opc.org) | In English | → Protestant churches | 
| OPC | Optical Proximity Correction | In English | → Graphic industries, printing, publishing | 
| OPC | Optimum Picture Control | In English | |
| OPCs | Oligodendrocyte Progenitor Cells | In English | → 5763 | 
| OPD | Optical Path Difference | In English | → Optics | 
| OPDAR | Optical Detection and Ranging | In English | → Optics | 
| OPDS | Organ on Politics, Defence and Security | In English | → International relations → Military affairs | 
| OPE | Operational Processing Equipment | In English | |
| OPEC | Organization of the Petroleum Exporting Countries = OPEP | Organisation des Pays Exportateurs de Pétrole | In French = OPEC | Organization of Petroleum Exporting Countries | In English = OPEL | Organizaĵo de Petrol-Eksportaj Landoj | In Esperanto = OPEP | Organização dos Países Exportadores de Petróleo | In Portuguese = OPEP | Organización de Países Esportadores de Petroleu | In Asturian = OPEP | Organización de Países Exportadores de Petróleo | In Spanish = OPEP | Organització de Països Exportadors de Petroli | In Catalan = ОПЕК | Организација на земји извознички на нафта и нафтени деривати | In Macedonian | In English | → Organizations and associations → Mining → 665 | 
| OPEC | Organization of Petroleum Exporting Countries = OPEP, OPEL, ОПЕК (look above) | In English | → Organizations and associations → Mining → 665 | 
| OPEIU | Office and Professional Employees International Union | In English | → Organizations and associations → Labour, labour economics | 
| OPEX | OPerational Expenditure | In English | → Accounting | 
| OPF | Orbiter Processing Facility | In English | → Astronautics | 
| OPGL | Osteoprotegerin Ligand | In English | → Biochemistry, biophysics | 
| OPI | Operations Procedure Instruction | In English | → Management | 
| OPI | Orbiter Payload Interrogator | In English | → Astronautics | 
| OPIDF | Operational Planning Identification File | In English | → Files → Management | 
| OPIS | Orbiter Prime Item Specification | In English | → Astronautics | 
| OPK | Ovulation Predictor Kit | In English | → Gynaecology → Reproductive biology | 
| OPL | Open Problem List | In English | |
| OPL | Orbiter Project Parts List | In English | → Astronautics | 
| OPL | Open Proxy List | In English | → Software → Networks, communication | 
| OPLF | Orbiter Processing and Landing Facility | In English | → Astronautics | 
| OPM | Operations Procedure Manual | In English | → Management | 
| OPM | Outer Planet Mission | In English | → Astronomy → Astronautics | 
| OPM | Office of Personnel Management | In English | → Personnel management | 
| OPML | Outline Processor Markup Language | In English | → Programming languages | 
| OPN | Osteopontin | In English | → Biochemistry, biophysics | 
| OPO | Orbiter Project Office | In English | → Astronautics | 
| OPOV | Oxidizer Preburner Oxidizer Valve | In English | → Vehicle engineering | 
| OPPAR | Orbiter Project Parts Authorization Request | In English | → Astronautics | 
| OPPF | Oxford Protein Production Facility | In English | → Biotechnology → Proteins | 
| OPPS | Operations Planning and Project Support | In English | → Management | 
| OPR | Office of Primary Responsibility | In English | → Management | 
| OPR | Operations Planning Review | In English | → Management | 
| OPR | Orbiter Payload Recorder | In English | → Astronautics | 
| OPR | Oxygen Pressure Regulator | In English | |
| OPRV | Oxygen Pressure Relief Valve | In English | |
| OPS | Operational Sequence | In English | → Management | 
| OPS | Orbiter Project Schedule | In English | → Astronautics | 
| OPS | Oxygen Purge System | In English | |
| OPSA | OSSTMM Professional Security Analyst | In English | → Computer science | 
| OpSCN | Optical Sciences Center Newsletter | In English | → Serial publications, periodicals → Optics | 
| OPSDB | Operations Data Base | In English | → Data | 
| OPSDBA | Operations Data Base Administrator | In English | → Data → Management | 
| OPSE | OSSTMM Professional Security Expert | In English | → Computer science | 
| OPSS | Orbital Propellant Storage Subsystem | In English | → Astronautics | 
| OPST | OSSTMM Professional Security Tester | In English | → Computer science | 
| OPT | Operational Pressure Transducer | In English | |
| OPTB | Operational Program Time Base | In English | |
| OptCo | Optics Communications | In English | → Serial publications, periodicals → Optics → Telecommunications | 
| OptEn | Optical Engineering | In English | → Serial publications, periodicals → Optics | 
| OptFT | Optical Fiber Technology | In English | → Serial publications, periodicals → Optics → Telecommunications | 
| OptL | Optics Letters | In English | → Serial publications, periodicals → Optics | 
| OptLE | Optics and Lasers in Engineering | In English | → Serial publications, periodicals → Optics → Electromagnetism | 
| OptLT | Optics Laser Technology | In English | → Serial publications, periodicals → Optics → Electromagnetism | 
| OptMa | Optical Materials | In English | → Serial publications, periodicals → Optics → Materials science | 
| OptN | Optics News | In English | → Serial publications, periodicals → Optics | 
| OptPE | Optical Physics and Engineering | In English | → Serial publications, periodicals → Optics | 
| OptPN | Optics & Photonics News | In English | → Serial publications, periodicals → Optics → Electromagnetism | 
| OptQE | Optical Quantum Electronics | In English | → Serial publications, periodicals → Quantum mechanics → Optics → Engineering, technology | 
| OptRv | Optical Review | In English | → Serial publications, periodicals → Optics | 
| OptSp | Optics and Spectroscopy | In English | → Serial publications, periodicals → Optics → Electromagnetism | 
| OPWC | Organisation for the Prohibition of Chemical Weapons (www.opcw.org) = OIAC | Organisation pour l'Interdiction des Armes Chimiques | In French | In English | → Organizations and associations → International relations → Military engineering | 
| OPWS | Orbital Payload Work Station | In English | → Astronautics | 
| OQE | Optical and Quantum Electronics | In English | → Serial publications, periodicals → Quantum mechanics → Optics → Engineering, technology | 
| OQL | Object Query Language | In English | → Programming languages → Data | 
| OR | Organized Research | In English | |
| ORA | Operational Requirements Analysis | In English | → Management | 
| ORAC | Oxygen Radical Absorbance Capacity | In English | → Biochemistry, biophysics → Nutrition | 
| ORAM | Output Random Access Memory | In English | → Memories | 
| ORB | Object Request Broker | In English | → Networks, communication | 
| ORB | Operations Review Board | In English | → Management | 
| ORC | Optical Character Recognition = ROC | Reconnaissance Optique de Caractères | In French | In English | → Writing systems → Computer-based techniques | 
| ORC | Operations Request Card | In English | |
| ORCHIS | Oak Ridge Computerized Hierarchical Information System | In English | → Computer science → Knowledge management | 
| ORCUS | Orbital Recording Capability and Update System | In English | → Astronautics | 
| ORD | Operational Readiness Data | In English | |
| ORD | Operational Ready Data | In English | |
| ORD | Operations Requirements Document | In English | → Management | 
| ORD | Orbital Requirements Document | In English | → Astronautics | 
| ORD | Office of Rare Diseases (http://rarediseases.info.nih.gov) | In English | → 345 → Pathology | 
| ORDBMS | Object-Relational Database Management System | In English | → Data | 
| ORDI | Ontology Representation and Data Integration | In English | → Software | 
| ORE | Output Request Element | In English | |
| ORF | Observer Research Foundation | In English | → Foundations | 
| ORFEUS | Observatories and Research Facilities for EUropean Seismology (http://orfeus.knmi.nl) | In English | → Research institutes → Seismology, earthquakes → Netherlands | 
| OrGeo | Organic Geochemistry | In English | → Serial publications, periodicals → Geochemistry | 
| ORI | Operational Readiness Inspection | In English | → Management | 
| ORI | Ocean Research Institute (www.ori.u-tokyo.ac.jp) | In English | → Research institutes → Marine research, oceanography → Japan | 
| ORIENT | Oriental Research Infrastructure to European Networks | In English | → Research policy → International relations | 
| ORIS | Office of Research and Information Systems | In English | → Knowledge management | 
| ORLA | Optimum Repair Level Analysis | In English | → Maintenance and logistics | 
| OrLi | Origins of Life | In English | → Serial publications, periodicals → Biological sciences | 
| ORM | Operational Reactivity Margin | In English | → 53912 → Nuclear technology | 
| ORP | OFS Retransmission Processor | In English | |
| ORP | Optional Retirement Program | In English | → Labour, labour economics | 
| ORR | Operational Readiness Review | In English | → Management | 
| ORR | Operations Requirements Review | In English | → Management | 
| ORRCA | Ontario Research Centre for Computer Algebra (www.orcca.on.ca) | In English | → Research institutes → Algebra → Computer science → Canada | 
| ORROE | Occasional Reports of the Royal Observatory Edinburgh | In English | → Serial publications, periodicals → Astronomy | 
| ORS | Outer Root Sheath | In English | → Anatomy | 
| ORS | Orbital Refueling System | In English | → Astronautics | 
| ORS | Orbital Reservicing System | In English | → Astronautics | 
| ORS | Orbital Resupply System | In English | → Astronautics | 
| ORSDI | Oak Ridge Selective Dissemination of Information | In English | → Computer science → Knowledge management | 
| ORT | Operational Readiness Test | In English | → Management | 
| ORT | Orbit Readiness Test | In English | → Astronautics | 
| ORU | Orbital Replaceable Unit | In English | → Astronautics | 
| ORU | Orbital Replacement Unit | In English | → Astronautics | 
| ORV | Orbital Research Vehicle | In English | → Astronautics | 
| OS | On-orbit Station | In English | → Astronautics | 
| OS | Operating Software | In English | → Software | 
| OS | Operating System | In English | → Operating systems | 
| OS | Orbiter CEI Specification | In English | → Astronautics | 
| OSA | Oklahoma Sociological Association | In English | → Associations → Sociology → United States | 
| OSA | Operational Support Area | In English | |
| OSA | Ordered-Subset Analysis | In English | |
| OSA | Operational Support Airlift | In English | |
| OSAJ | Optical Society of America Journal | In English | → Serial publications, periodicals → Optics → United States | 
| OSAJI | Optical Society of America Journal - Optics and Image Science | In English | → Serial publications, periodicals → Optics → United States | 
| OSALL | Organisation of South African Law Libraries | In English | → Organizations and associations → Libraries → Law, jurisprudence → Africa | 
| OSART | Operational Safety Assessment Review Team | In English | → Nuclear technology | 
| OSB | Order of Saint Benedict | In English | → Roman catholic church | 
| OSB | Orientated Strand Board | In English | → Timber and woodworking industry | 
| OSC | Orbital Sciences Corporation | In English | → Astronautics | 
| OSC | Order of Saint Camillus | In English | → Roman catholic church | 
| OSC | Operations Support Center | In English | |
| OSC | Operations Support Contract | In English | |
| OSC | Optical Signatures Code | In English | |
| OSCAR | Orbiting Satellite Carrying Amateur Radio | In English | → Astronautics → Telecommunications |