| O | the 15th letter of the Roman alphabet |
|---|---|
| O | the blood group whose red cells carry neither the A nor B antigens |
| O | a nonmetallic bivalent element that is normally a colorless odorless tasteless nonflammable diatomic gas |
| O | (England) the basic level of a subject taken in school |
| O | a gasket consisting of a flat ring of rubber or plastic |
| O | Irish writer (born in 1932) |
| O | Irish playwright (1880-1964) |
| O | according to the clock |
| O | United States writer (1925-1964) |
| O | throughout a period of time |
| O | Irish writer of short stories (1896-1984) |
| O | United States writer (1905-1970) |