1. [ noun ] (immunology) the blood group whose red cells carry neither the A nor B antigens
Synonyms: group_O type_O

"people with type O blood are universal donors"

Related terms: blood_group
2. [ noun ] (chemistry) 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
Related terms: gas chemical_element liquid_oxygen air water ozone oxygenize oxygenate
3. [ noun ] the 15th letter of the Roman alphabet
Related terms: letter Roman_alphabet
Similar spelling:   ow