| OC | Optical Carrier | - | Human Genome |
| OCR | Optical Character Recognition | - | Human Genome |
| OCX | OLE Custom Control | - | Human Genome |
| ODBC | Open Database Connectivity | - | Human Genome |
| ODI | Open Data-link Interface | - | Human Genome |
| OEM | Original Equipment Manufacturer | - | Human Genome |
| OIM | Open Information Model | - | Human Genome |
| OLAP | Online Analytical Processing | - | Human Genome |
| OLE | Object Linking And Embedding | - | Human Genome |
| OLED | Organic Light-Emitting Diode | - | Human Genome |
| OLTP | On-Line Transaction Processing | - | Human Genome |
| OMG | Object Management Group | - | Human Genome |
| OMG | Oh My God | - | Human Genome |
| OOP | Object-Oriented Programming | - | Human Genome |
| OPENSRS | Open Shared Registration System | - | Human Genome |
| OPSEC | Open Platform For Secure Enterprise Connectivity Alliance | - | Human Genome |
| OSF | Open Software Foundation | - | Human Genome |
| OSI | Open System Interconnection | - | Human Genome |
| OSPF | Open Shortest Path First | - | Human Genome |
| OSR | OEM System Release | - | Human Genome |
| OTOH | On The Other Hand | - | Human Genome |
| OA | optical amplifier
| - | Human Genome |
| OADM | optical add-drop multiplexer
| - | Human Genome |
| OAM | operations, administration, and management
| - | Human Genome |
| OAMP | one-way active measurement protocol
| - | Human Genome |
| OAM&P | operations, administration, maintenance and provisioning
| - | Human Genome |
| OCD | operational capability demonstration
| - | Human Genome |
| OCDD | online call detail data
| - | Human Genome |
| OCN | Operating Company Number
| - | Human Genome |
| OC-N | optical carrier level-N
| - | Human Genome |
| OCONUS | outside contiguous United States
| - | Human Genome |
| OCP | optical control plane
| - | Human Genome |
| OEO | optical-electrical-optical
| - | Human Genome |
| OFDM | orthogonal frequency division multiplexing
| - | Human Genome |
| OGP | Office of Government-wide Policy
| - | Human Genome |
| OIF | Optical Internetworking Forum
| - | Human Genome |
| OMB | Office of Management and Budget
| - | Human Genome |
| ON | optical networking
| - | Human Genome |
| OOB | out-of-band
| - | Human Genome |
| OPM | Office of Personnel Management
| - | Human Genome |
| OPS | One-Way Paging Service
| - | Human Genome |
| OPT | Office of Priority Telecommunications
| - | Human Genome |
| ORT | operations readiness test
| - | Human Genome |
| OS | operating system
| - | Human Genome |
| OSE | open system environment
| - | Human Genome |
| OSNR | optical-signal to-noise ratio
| - | Human Genome |
| OSS | operational support system
| - | Human Genome |
| OSWF | onsite workforce
| - | Human Genome |
| OTA | over the air
| - | Human Genome |
| OTAR | over-the-air-rekeying
| - | Human Genome |
| OTC | Office of the TSP Coordinator
| - | Human Genome |
| OTDR | optical time domain reflectometer
| - | Human Genome |
| OTGR | optical transport generic requirements
| - | Human Genome |
| OTM | Office of Transition Management
| - | Human Genome |
| OTM(SONET) | optical terminal multiplexer
| - | Human Genome |
| OTN | optical transport network
| - | Human Genome |
| OVO | open view operations
| - | Human Genome |
| OVPN | optical virtual private network
| - | Human Genome |
| OWS | Optical Wavelength Service
| - | Human Genome |
| OSLS | Open Source Library Software
| - | Human Genome |
