Definition of 'o'
- a nonmetallic bivalent element that is normally a colorless odorless tasteless nonflammable diatomic gas; constitutes 21 percent of the atmosphere by volume; the most abundant element in the earth's crust
Synonyms: oxygen atomic number 8
- the 15th letter of the Roman alphabet
Synonyms: letter o
- the blood group whose red cells carry neither the A nor B antigens; "people with type O blood are universal donors"
Synonyms: type O group O