O

• (noun) the blood group whose red cells carry neither the A nor B antigens

  "people with type O blood are universal donors"

  synonyms : group o , type o

• (noun) the 15th letter of the Roman alphabet

• (noun) 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 : atomic number 8 , oxygen

WordNet® 3.0, © 2006 by Princeton University.

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