| onze | onze |
| onze cent | mil e cem |
| onze heures | onze |
| onze novembre | Dia do Ex-combatente |
| onzième | décimo-primeiro |
| onéreux | pesado |
| OO | OO |
| Oolon | Oolong |
| Oompa Loompa | Oompa-Loompas |
| Oomycota | Oomycota |
| OP | Ordem dos Pregadores |
| Op Art | Op art |
| Opabinia | Opabínia |
| opacité | obscuridade |
| opale | opala |
| opalescence | opalescência |
| opalescent | opalescente |
| opaque | confuso |
| Opatija | Opatija |
| Opel | Opel |
| Opel Astra G | Astra |
| Opel Astra H | Astra |
| Opel Meriva | Meriva |
| Opel Vectra | Opel Vectra |
| Opel Zafira | Opel Zafira |
| Open database connectivity | ODBC |
| Open de Bâle | Swiss Indoors |
| Open de France de badminton | Torneio de Roland-Garros |
| Open Directory Project | Open Directory Project |
| Open du Brésil | Brasil Open de Tênis |
| Open du Canada | Canada Masters |
| Open Group | The Open Group |
| Open shortest path first | Open Shortest Path First |
| Open Source | Software livre |
| Open Source Definition | Licença de software livre |
| Open Your Heart | Open Your Heart |
| OpenLaszlo | Laszlo |
| OpenMosix | OpenMosix |
| OpenNap | OpenNap |
| OpenPGP | OpenPGP |
| OpenSolaris | OpenSolaris |
| OPENSTEP | OpenStep |
| OpenSUSE | OpenSUSE |
| OPEP | Organização dos Países Exportadores de Petróleo |
| Opera | Opera |
| Opera enregistre des téléchargements records depuis mardi | Downloads do Opera batem recorde |
| Opera Garnier | Òpera Garnier |
| Opera Software | Opera Software |
| Operación Triunfo | Operação Triunfo |
| Operation Barbarossa | Operacao Barbarossa |
| OPEX | OPEX |
| Opfertshofen | Opfertshofen |
| Ophel | Ophel |
| Ophichthidae | Ophichthidae |
| Ophidiiformes | Ophidiiformes |
| Ophion | Ofion |
| Ophiuchus | Ophiuchus |
| Ophiuroidea | Ophiuroidea |
| Ophrys abeille | Erva-abelha |
| Ophrys apifera | Erva-abelha |
| ophtalmique | oftálmico |
