The phrase “OB marker” cannot be found in the Oxford Online Dictionary. Nor can it be found in OxfordDictionaries.com, which updates much faster and just added new words such amazeballs and douchebaggery to its list.
An OB marker, short for ‘out of bounds marker’ is a term used in Singapore to denote what topics are permissible for public discussion. The full form of the word is rarely used.
The term is adopted from golf, where an out of bounds marker denotes the area beyond which playing is not allowed… The term “OB markers” was first used in 1991 by the then-Minister for Information and the Arts George Yeo to describe the boundaries of acceptable political discourse.