| o association ... O'Neill, Owen Roe |
| O'Neill, Rose Cecil ... Obama, Michelle |
| oban ... obole |
| Obolellida ... oceanic crust |
| Oceanic dance ... Ocypode ceratophthalmus |
| Ocypode saratan ... Oerter, Al |
| Oeser, Adam Friedrich ... Ogunde Concert Party |
| Ogunde, Hubert ... Oise Lateral Canal |
| Oise River ... Okuma Kotomichi |
| Okuma Shigenobu ... Old Javanese language |
| Old Khmer language ... Oldroyd, James Gardner |
| Olds, James ... Oliveira, Carlos de |
| Oliveira, Manoel de ... Olympic, Operation |
| Olympio, Gilchrist ... on side |
| On'ami ... online publishing |
| online system ... Open Handset Alliance |
| open pan sugar ... Opheliida |
| Opheltes ... optical brightener |
| optical ceramics ... oral pathology |
| oral pharynx ... orc |
| Orcagna, Andrea ... ore reserve |
| Oread ... organized resistance movement |
| organized storm ... Orionid meteor shower |
| oriori ... ornithosuchian |
| Ornithurae ... orthoconglomerate |
| orthodontics ... Osborn, Mount |
| Osborn, Sherard ... osmotic pressure |
| osmotrophy ... Ostpolitik |
| ostraca ... Otomo Yakamochi |
| Otophryninae ... Ouham River |
| Ouida ... outpatient department |
| output ... overt idolatry |
| overthrust ... oxepine |
| oxetane ... oyster crab |
| oyster drill ... |
|
|
