What does OO stand for?

Belgium - International civil aircraft marking (ODBW)

Naval Oceanographic Office - Also known as NOO; formerly, HO, NHO, USNHO

Oakly, Inc. - NYSE symbol (SAG)

Oberlin College, Oberlin, OH - Library symbol - Library of Congress (LCLS)

Object Orientation

Object-Oriented (BYTE)

Observation Officer - Military

Oceanic Operators (SAUS)

Oceanographic Office

Ocean Outlook (EA)

Office of Operations - Department of Agriculture (GFGA)

Office of Outreach

Ohio Opinions - A publication (DLA)

Ohne Ort - Without Place of Publication - Bibliography - German

Old Orkney - Whisky (ROG)

Once Over - To examine cursorily - Slang

On Order

Oophorectomized - Gynecology

Open Order

Operation Office (SAUS)

Operation Order - Military

Operations Office - Environmental Protection Agency (GFGA)

Operations Officer - Navy - British

Optical Orientation (SAUS)

Oral Order (SAUS)

Orbiting Observatory (SAUS)

Orderly Officer - British

Ordnance Office - Firearms use code - Firearms collecting (FAUC)

Ordnance Office - or Officer

Orthopaedics Overseas (EA)

Osobyi Otdel - Counterintelligence surveillance unit in military formation until 1943 - Former USSR

Otoe-Missouria - NCIC Indian nation code (NCIC)

Owner's Option (RIMS)

Own Occupation - Banking

Skywest Airlines (SAUS)

Sunaire Lines - ICAO designator (AD)