| Meaning | Explication | Aliases | Taxon | |
|---|---|---|---|---|
| <office> | Artifacts | Show shifts | ||
| <orthopteran> | Animals | Show shifts | ||
| oak | deciduous tree with distinctive deeply lobed leaves, acorns, and notably strong wood, typically of England and northeastern North America, included in genus Quercus. | Plants | Show shifts | |
| oar | type of lever used to propel a boat, having a flat blade at one end and a handle at the other, and pivoted in a rowlock atop the gunwale, whereby a rower seated in the boat and pulling the handle can pass the blade through the water by repeated strokes against the water's resistance, thus moving the boat | Artifacts | Show shifts | |
| oat | widely cultivated cereal grass, typically Avena sativa | Plants | Show shifts | |
| oath | N/a | Show shifts | ||
| obedient | willing to comply with the commands, orders, or instructions of those in authority | N/a | Show shifts | |
| objection, contradiction | N/a | Show shifts | ||
| observer | Human being | Show shifts | ||
| obsidian | naturally occurring volcanic glass formed when lava extruded from a volcano cools rapidly with minimal crystal growth | N/a | Show shifts | |
| obstacle | something that impedes progress or achievement (Merriam-Webster) | N/a | Show shifts | |
| obstinate, persistent | None | Non-physical | Show shifts | |
| ocean | one of the large bodies of water separating the continents | N/a | Show shifts | |
| ochre | N/a | Show shifts | ||
| October | tenth month of the Gregorian calendar, following September and preceding November | N/a | Show shifts | |
| oesophagus | tube that carries food from the pharynx to the stomach | N/a | Show shifts | |
| of high rank | Non-physical | Show shifts | ||
| of low rank | None | Non-physical | Show shifts | |
| official (n.) | N/a | Show shifts | ||
| offspring | N/a | Show shifts | ||
| often | N/a | Show shifts | ||
| oil (food) | Artifacts | Show shifts | ||
| oil particle | Natural objects | Show shifts | ||
| ointment | (medicine) A viscous preparation of oils and/or fats, usually containing medication, used as a treatment or as an emollient | N/a | Show shifts | |
| OK | expression used to indicate acceptance | Abstract relations | Show shifts | |
| old (vs. new) | existing, created a long time ago | Time | Show shifts | |
| old (vs. young) | having lived for most of the expected years | Time | Show shifts | |
| old man | Human being | Show shifts | ||
| old man/grandfather | old man and grandfather | N/a | Show shifts | |
| old woman | Human being | Show shifts | ||
| oleander | N/a | Show shifts | ||
| olive (Olea europaea) | N/a | Show shifts | ||
| omen | Abstract entities | Show shifts | ||
| on all fours | on one's hands and knees | N/a | Show shifts | |
| on the outside | Space | Show shifts | ||
| once | N/a | Show shifts | ||
| one (unit) | Abstract entities | Show shifts | ||
| one hundred thousand | N/a | Show shifts | ||
| one piece (at counting) | Abstract entities | Show shifts | ||
| one's own | N/a | Show shifts | ||
| onion | N/a | Show shifts | ||
| only, just | Abstract entities | Show shifts | ||
| open (adj.) | Other physical | Show shifts | ||
| open-eyed | with open eyes | N/a | Show shifts | |
| opening of a sack | N/a | Show shifts | ||
| opening, hole | Natural objects | Show shifts | ||
| operculum of a snail | anatomical structure like a trapdoor that exists in many (but not all) groups of sea snails and freshwater snails, and also in a few groups of land snails | N/a | Show shifts | |
| opinion | Abstract entities | Show shifts | ||
| opossum | Animals | Show shifts | ||
| opportunity | Abstract entities | Show shifts | ||
| opposite | Non-physical | Show shifts | ||
| orange (plant) | N/a | Show shifts | ||
| orator | N/a | Show shifts | ||
| order | N/a | Show shifts | ||
| ordinary, common | N/a | Show shifts | ||
| oregano | N/a | Show shifts | ||
| organ (anatomy) | larger part of an organism, composed of tissues that perform similar functions | N/a | Show shifts | |
| origin | None | Abstract entities | Show shifts | |
| original | N/a | Show shifts | ||
| orphan | N/a | Show shifts | ||
| osprey (Pandion haliaёtus) | N/a | Show shifts | ||
| ostrich | Animals | Show shifts | ||
| other | Non-physical | Show shifts | ||
| other`s | Non-physical | Show shifts | ||
| otter (Lutra lutra) | Animals | Show shifts | ||
| outbuilding | N/a | Show shifts | ||
| outwards | N/a | Show shifts | ||
| oven | N/a | Show shifts | ||
| overcoat | Artifacts | Show shifts | ||
| owl | Animals | Show shifts | ||
| own (of a relative) | Non-physical | Show shifts | ||
| owner | Human being | Show shifts | ||
| owner (female) | N/a | Show shifts | ||
| owre, buffalo (Bubalus bubalis) | Animals | Show shifts | ||
| ox | N/a | Show shifts |