- oxygenThe chemical element (symbol O) with an atomic number of 8 and relative atomic mass of 15.9994. It is a colorless and odorless gas. Sometimes called elemental oxygen to distinguish it from molecular oxygen.
- amphioxusThe lancelet, particularly of the genus Branchiostoma.
- oxicSharp; pointy.
- oxy-Sharp, keen, acute, pungent, acid
- oxytropeSynonym of locoweed.