| ovationner | applaud |
| Ove Høegh-Guldberg | Ove Høegh-Guldberg |
| Over the Hills and Far Away | Over the Hills and Far Away |
| Over-blowing | Overblowing |
| overdose | overdose |
| Overhead | Computational overhead |
| Overijssel | Overijssel |
| Overijsselse Vecht | Vechte |
| Overseas Union Bank Centre | OUB Centre |
| Overijssel | Overijssel |
| Ovid Densuşianu | Ovid Densusianu |
| Ovide | Ovid |
| Ovide Decroly | Ovide Decroly |
| Ovidiu Stângă | Ovidiu Stîngă |
| oviducte | Fallopian tube |
| ovidé | ovine |
| Oviedo | Oviedo |
| ovipare | oviparous |
| Oviparité | Egg |
| Oviraptor | Oviraptor |
| Oviraptorosauria | Oviraptorosauria |
| Ovis | Ovis |
| Ovis canadensis sierrae | Sierra Nevada Bighorn Sheep |
| ovni | UFO |
| ovniologie | ufology |
| ovniologue | ufologist |
| Ovomaltine | Ovaltine |
| ovoïdal | egg-shaped |
| ovoïde | egg-shaped |
| ovulation | ovulation |
| ovule | ovum |
| ovuler | ovulate |
| Ovulidae | Ovulidae |
| Owain Glyndŵr | Owain Glyndŵr |
| Owain Gwynedd | Owain Gwynedd |
| Owain le Rouge | Owain Goch ap Gruffydd |
| Owain mab Urien | Owain mab Urien |
| Owen | Owen |
| Owen Arthur | Owen Arthur |
| Owen Barfield | Owen Barfield |
| Owen Chamberlain | Owen Chamberlain |
| Owen Roberts | Owen Josephus Roberts |
| Owen Willans Richardson | Owen Willans Richardson |
| Owen Wilson | Owen Wilson |
| Owhyee | Owhyee |
| OWL | Owl |
| Ox | Samer el Nahhal |
| Oxalidaceae | Oxalidaceae |
| Oxalidales | Oxalidales |
| Oxaliplatine | Oxaliplatin |
| Oxalis corniculée | Oxalis corniculata |
| Oxalis stricta | Oxalis stricta |
| Oxalá | Obatala |
| Oxelösund | Oxelösund Municipality |
| Oxfam | Oxfam |
| Oxfam international | Oxfam |
| Oxford | Oxford |
| Oxford Circus | Oxford Circus tube station |
| Oxford English Dictionary | Oxford English Dictionary |
| Oxford Street | Oxford Street |
| Oxfordien | Oxonian |
| Oxfordshire | Oxfordshire |
| oxiranne | ethylene oxide |
| Oxycodone | Oxycodone |
| oxydant photochimique | photochemical oxidant |
| oxydation | oxidation |
