| Orbite | Orbit |
| Orbite circolari | Circular orbits |
| Orbite eccentriche | Eccentric orbit |
| Orbite eliocentriche | Heliocentric orbits |
| Orbite ellittiche | Elliptical orbit |
| Orbite geocentriche | Geocentric orbits |
| Orbite iperboliche | Hyperbolic orbits |
| Orbite Kepleriane | Keplerian orbit |
| Orbite osculatrici | Osculating orbit |
| Orbite paraboliche | Parabolic orbit |
| Orbite periodiche | Periodic orbits |
| Orbite polari | Polar orbit |
| Orbiter | Space Shuttle Orbiter |
| orca | orc |
| Orcaella brevirostris | Irrawaddy Dolphin |
| Orcaella heinsohni | Australian Snubfin Dolphin |
| Orcagna | Orcagna |
| orchestra | orchestra |
| Orchestra Baobab | Orchestre Baobab |
| orchestrale | orchestral |
| orchestrare | foster |
| orchestrazione | orchestration |
| orchetto vellutato | velvet scoter |
| Orchidaceae | Orchidaceae |
| Orchidacee | Orchidaceae |
| Orchidales | Orchidales |
| orchidea | orchid |
| Orchidea bionda | Ladies of the Chorus |
| Orchis lactea | Orchis lactea |
| Orchis militaris | Military Orchid |
| Orchis morio | Green-winged Orchid |
| Orchis papilionacea | Orchis papilionacea |
| Orchis provincialis | Orchis provincialis |
| Orchis purpurea | Lady orchid |
| Orchis ustulata | Burnt orchid |
| orci | tankards |
| orcia | jug |
| Orcinus orca | Orca |
| orcio | jar |
| orco | giant |
| Orcomeno | Orchomenos |
| Orconectes limosus | Orconectes limosus |
| Orcoyen | Orcoyen |
| orda | horde |
