Olympic Games, an international multi-sport event taking place every four years

Austria, from its World Meteorological Organization country code

Operating system, the software that manages the hardware and software of a computer

Open Source software

Osmium, a chemical element

Old Style date, referring to the Julian Calendar; see Old Style and New Style dates

Ordnance Survey the national mapping agency for Great Britain

one of the Æsir

Outlaw Star, a popular Japanese anime

Ossetian language, from its ISO 639 alpha-2 code

Open Seat, a tennis tournament in Barecelona, Spain

Off Screen; a formatting abbreviation in screenplays.

Old Stoic, a former pupil of Stowe School

Old Sedberghian, a former pupil of Sedbergh School

Austrian Airlines, its IATA code

Old Shirburnian, a former pupil of Sherborne School

Os, Hordaland, a municipality in Norway

External orifice of the uterus, the external os

Ansuz rune, an Anglo-Saxon rune

Internal orifice of the uterus, the internal os

Os, Hedmark, a municipality in Norway

Ogawa Seiki, a Japanese manufacturer of model airplane engines

Overseas, meaning literally a place over a sea, is synonymous in some countries with the word international. For example, someone in New York City might consider Toronto overseas, even though they are on the same...

Os, Østfold, a parish in Norway.

Orba Squara - stage name of Mitch Davis, singer/songwriter