Real Dictionary

O.B. in American English
abbreviation: opening of books

OB in American English
obstetrician
abbreviation: obstetrical

Ob in American English 1
river in W Siberia, flowing from the Altai Mountains northwest & north into the Gulf of Ob: 2,495 mi (4,015 km)

Ob in American English 2
Obadiah

Ob in British English
abbreviation for: Old Boy
noun: a river in N central Russia, formed at Bisk by the confluence of the Biya and Katun Rivers and flowing generally north to the Gulf of Ob (an inlet of the Arctic Ocean): one of the largest rivers in the world, with a drainage basin of about 2 930 000 sq km

ob- in American English
to, toward, before, in front of
prefix: a prefix meaning “toward,” “to,” “on,” “over,” “against,” orig. occurring in loanwords from Latin, but now used also, with the sense of “reversely,” “inversely,” to form Neo-Latin and English scientific terms

ob- in British English
prefix: inverse or inversely

ob. in American English
he (or she) died
abbreviation: he died; she died

ob. in British English
abbreviation for: (on tombstones) obiit