| O/E | Observed Number/expected Number Ratio = Relative Risk | - | Computer Acronyms(common) |
| OA | Office Of The Administrator | - | Computer Acronyms(common) |
| OAM | Optical Absorption Microscope | - | Computer Acronyms(common) |
| OAO | Orthogonalized Atomic Orbital | - | Computer Acronyms(common) |
| OAP | Optical Atom Probe | - | Computer Acronyms(common) |
| OAPP | Oxidized Atactic Polypropylene | - | Computer Acronyms(common) |
| OAQPS | Office Of Air Quality Planning And Standards | - | Computer Acronyms(common) |
| OAQPSTTN | Office Of Air Quality Planning And Standards Technology Transfer Network | - | Computer Acronyms(common) |
| OAR | Office Of Air And Radiation (USEPA) | - | Computer Acronyms(common) |
| OARM | Office Of Administration And Resources Management (USEPA) | - | Computer Acronyms(common) |
| OASCR | Office Of Advanced Scientific Computing Research | - | Computer Acronyms(common) |
| OASIS | Ocean And Atmospheric Sounding Interferometer System | - | Computer Acronyms(common) |
| OASLM | Optically Addressed Spatial Light Modulator | - | Computer Acronyms(common) |
| OAW | Oxyacetylene Welding | - | Computer Acronyms(common) |
| OB/OD | Open Burn/open Detonation | - | Computer Acronyms(common) |
| OBD | Optical Beam Deflection | - | Computer Acronyms(common) |
| OBD | On-board Diagnosis | - | Computer Acronyms(common) |
| OBDD | Ordered Bicontinuous Double-diamond | - | Computer Acronyms(common) |
| OBE | Optical Bloch Equation | - | Computer Acronyms(common) |
| OBIC | Optical Beam Induced Current | - | Computer Acronyms(common) |
| OBK | Oppenheimer-Brinkman-Kramers (approxn. In Atom-ion Electron-exchange Calcns.) | - | Computer Acronyms(common) |
| OBK2 | Second-order Oppenheimer-Brinkman-Kramers | - | Computer Acronyms(common) |
| OBK3 | Third-order Oppenheimer-Brinkman-Kramers | - | Computer Acronyms(common) |
| OBS-MCSC | Optimized Basis Set-multiconfiguration Spin Coupled | - | Computer Acronyms(common) |
| OC | Office Of The Comptroller | - | Computer Acronyms(common) |
| OC | Oxygen Consumed | - | Computer Acronyms(common) |
| OCAMS | Orbital Correspondence Analysis In Maximum Symmetry | - | Computer Acronyms(common) |
| OCAP | Open-channel Air Preheater | - | Computer Acronyms(common) |
| OCBSE | Orthogonality Constrained Basis Set Expansion Prodedure | - | Computer Acronyms(common) |
| OCC | Organochlorinated Compound | - | Computer Acronyms(common) |
| OCCSD | Open-shell Coupled-cluster (with) Single (and) Double (excitations) | - | Computer Acronyms(common) |
| OCD | Offshore And Coastal Dispersion (modeling Of Air Quality) | - | Computer Acronyms(common) |
| OCD | Overlapping Charge Density (model In Electronic Structure) | - | Computer Acronyms(common) |
| OCE | One-center Expansion (SCF MO Method) | - | Computer Acronyms(common) |
| OCE | Overall Control Efficiency | - | Computer Acronyms(common) |
| OCE-DF | One-center Expansion Dirac-Fock | - | Computer Acronyms(common) |
| OCEC | Open-channel Electrochromatography | - | Computer Acronyms(common) |
| OCEE | Overlap Corrected Electronegativity Equalization | - | Computer Acronyms(common) |
| OCEFT | Office Of Criminal Enforcement | - | Computer Acronyms(common) |
| OCEPA | Office Of Communications | - | Computer Acronyms(common) |
| OCH | Ochkur (approxn. In Electron-atom Scattering Calcns.) | - | Computer Acronyms(common) |
| OCIS | OSHA Computerized Information System | - | Computer Acronyms(common) |
| OCIS | Optics Classification And Indexing Scheme | - | Computer Acronyms(common) |
| OCLC | Online Computer Library Center | - | Computer Acronyms(common) |
| OCOS | Orbital Charge-ordering State | - | Computer Acronyms(common) |
| OCP | Organochlorine Pesticide | - | Computer Acronyms(common) |
| OCPSF | Organic Chemical, Plastics, And Synthetic Fiber Industry | - | Computer Acronyms(common) |
| OCR | Optical Character Recognition | - | Computer Acronyms(common) |
| OCRWM | Office Of Civilian Radioactive Waste Management | - | Computer Acronyms(common) |
| OCS | Outer Continental Shelf | - | Computer Acronyms(common) |
| OCSC | Orbital-charge-self-consistent (in Electronic State Calcn.) | - | Computer Acronyms(common) |
| OCT | Optical Coherence Tomography | - | Computer Acronyms(common) |
| OCT | Optical Current Transducer | - | Computer Acronyms(common) |
| OCT | Optimized Cluster Theory | - | Computer Acronyms(common) |
| OCTA | Oxidizing Capacity Of The Tropospheric Atmosphere | - | Computer Acronyms(common) |
| OCTG | Oil Country Tubular Goods | - | Computer Acronyms(common) |
| OCTS | Ocean Color And Temperature Sensor | - | Computer Acronyms(common) |
| OD | Order-Disorder (in Mineral Structure) | - | Computer Acronyms(common) |
| OD | Optical Density | - | Computer Acronyms(common) |
| ODAS | Ocean Data Acquisition System | - | Computer Acronyms(common) |
| ODC | Optimized Double Configuration | - | Computer Acronyms(common) |
| ODC | Orientation Distribution Coeffs. | - | Computer Acronyms(common) |
| ODC | Ozone Depleting Chemical | - | Computer Acronyms(common) |
| ODCPA | Off-diagonal (disorder) Coherent-potential Approxn. | - | Computer Acronyms(common) |
| ODES | Ocean Data Evaluation System | - | Computer Acronyms(common) |
| ODEX | Optical Dynamics Experiments | - | Computer Acronyms(common) |
| ODF | Orientation Distribution Function | - | Computer Acronyms(common) |
| ODFS | Optimized Dirac-Fock-Slater | - | Computer Acronyms(common) |
| ODLRO | Off-diagonal Long-range Order | - | Computer Acronyms(common) |
| ODLTS | Optical Deep Level Transient Spectroscopy | - | Computer Acronyms(common) |
| ODMR | Optically Detected Magnetic Resonance | - | Computer Acronyms(common) |
| ODP | Ocean Drilling Program | - | Computer Acronyms(common) |
| ODP | Optical Deformation Potential | - | Computer Acronyms(common) |
| ODP | Ozone Depletion Potential | - | Computer Acronyms(common) |
| ODPA | 4,4'-oxydiphthalic Anhydride | - | Computer Acronyms(common) |
| ODPAS | Optically Detected Photoacoustic Spectroscopy | - | Computer Acronyms(common) |
| ODR | Optical Double Resonance | - | Computer Acronyms(common) |
| ODS | Oxide Dispersion-strengthened | - | Computer Acronyms(common) |
| ODS | Ozone Depleting Substances | - | Computer Acronyms(common) |
| ODSC | Oscillating Differential Scanning Calorimetry | - | Computer Acronyms(common) |
| ODT | Order-disorder Transition | - | Computer Acronyms(common) |
| ODU | Optical Density Units | - | Computer Acronyms(common) |
| ODUS | Ozone Dynamics UV Spectrometer | - | Computer Acronyms(common) |
| OE | Office Of Enforcement | - | Computer Acronyms(common) |
| OEA | Occupational Exposure Assessment | - | Computer Acronyms(common) |
| OEAO | Overlap Enhanced Atomic Orbital | - | Computer Acronyms(common) |
| OEBR | Optical Edge Bead Removal | - | Computer Acronyms(common) |
| OECA | Office Of Enforcement And Compliance Assurance | - | Computer Acronyms(common) |
| OECD | Organization For Economic Cooperation And Development | - | Computer Acronyms(common) |
| OECD/SIDS | Organisation For Economic Co-operation And Developments Screening Information Data Sets | - | Computer Acronyms(common) |
| OEH | One-electron Hamiltonian (quantum Method) | - | Computer Acronyms(common) |
| OEIC | Optoelectronic Integrated Circuit | - | Computer Acronyms(common) |
| OEL | Occupational Exposure Limit | - | Computer Acronyms(common) |
| OELD | Organic Electroluminescent Device | - | Computer Acronyms(common) |
| OEM | Original Equipment Manufacturer | - | Computer Acronyms(common) |
| OEMO | One Electron Molecular Orbital | - | Computer Acronyms(common) |
| OEMTB | One-electron Mol. Tight-binding (for Electronic Structure) | - | Computer Acronyms(common) |
| OEO | Overlap-enhanced Orbital | - | Computer Acronyms(common) |
| OEP | Odd-even (alkane/carbon) Predominance (geology) | - | Computer Acronyms(common) |
| OEP | Optimized Effective-potential (quantum Method) | - | Computer Acronyms(common) |
