Orinoco River
— Noun
– English
~ a South American river 1,500 miles long; flows into the South Atlantic
Orange River
— Noun
– English
~ a river in South Africa that flows generally westward to the Atlantic Ocean
Ottawa river
— Noun
– English
~ a river in southeastern Canada that flows along the boundary between Quebec and Ontario to the Saint Lawrence River near Montreal
Ouachita River
— Noun
– English
~ a river that rises in western Arkansas and flows southeast into eastern Louisiana to become a tributary of the Red River
Ouse River
— Noun
– English
~ a river in northeastern England that flows generally southeastward to join the Trent River and form the Humber
Osage River
— Noun
– English
~ a river in Missouri that is a tributary of the Missouri River
Ohio River
— Noun
– English
~ a river that is formed in western Pennsylvania and flows westward to become a tributary of the Mississippi River
Oder River
— Noun
– English
~ a European river; flows into the Baltic Sea
oriental roach
— Noun
– English
~ dark brown cockroach originally from orient now nearly cosmopolitan in distribution
off-roader
— Noun
– English
~ a bicycle with a sturdy frame and fat tires; originally designed for riding in mountainous country
Otto Robert Frisch
— Noun
– English
~ British physicist (born in Austria) who with Lise Meitner recognized that Otto Hahn had produced a new kind of nuclear reaction which they named nuclear fission; Frisch described the explosive potential of a chain nuclear reaction (1904-1979)
Oral Roberts
— Noun
– English
~ United States evangelist (born 1918)
Oscar Robertson
— Noun
– English
~ United States basketball guard (born in 1938)
oysters Rockefeller
— Noun
– English
~ oysters spread with butter and spinach and seasonings and baked on the half shell
order Rodentia
— Noun
– English
~ small gnawing animals: porcupines; rats; mice; squirrels; marmots; beavers; gophers; voles; hamsters; guinea pigs; agoutis
onion roll
— Noun
– English
~ yeast-raised roll flavored with onion
operating room
— Noun
– English
~ a room in a hospital equipped for the performance of surgical operations; "great care is taken to keep the operating rooms aseptic"
order Rosales
— Noun
– English
~ in some classifications this category does not include Leguminosae