List of acronyms: O

This list contains acronyms, initialisms, and pseudo-blends  that begin with the letter O.

For the purposes of this list:

  • acronym = an abbreviation pronounced as if it were a word, e.g., SARS = severe acute respiratory syndrome, pronounced to rhyme with cars
  • initialism = an abbreviation pronounced wholly or partly using the names of its constituent letters, e.g., CD = compact disc, pronounced cee dee
  • pseudo-blend = an abbreviation whose extra or omitted letters mean that it cannot stand as a true acronym, initialism, or portmanteau (a word formed by combining two or more words).
(a) = acronym, e.g.: SARS – (a) severe acute respiratory syndrome
(i) = initialism, e.g.: CD – (i) compact disc
(p) = pseudo-blend, e.g.: UNIFEM – (p) United Nations Development Fund for Women
(s) = symbol (none of the above, representing and pronounced as something else; for example: MHz – Megahertz)

(Main list of acronyms)


  • O – (i) Oberst – Observer – Obstacle – Octal – Officer – Official – Oh – Operational – Operator – Oprah (magazine) – Outstanding – (s) Oxygen

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  • ob – (p) obiit (Latin, "(s) he died")
  • OB – (p) Obedience – Obligation – Obligatory – Obsolete – Obstetrics – (i) Ocean Beach (California) – Off Break (cricket) – Old Bryanstonian – Order of Battle – Outlet Box (electrical) – (p) Overbought (stock market) – (i) Oversight Board
  • OBE – (i) Officer of the Order of the British Empire
  • OBJ – (p) Objective (military parlance)
  • OBM – (p) Obsidian Black Metallic (automobile paint color)
  • OBS – (p) Observation/Observer – Obsolete – Obstacle – (i) Off Balance Sheet – Optical Burst Switching (IEEE) – Organic Brain Syndrome – Organization(al) Breakdown Structure
  • OBSS – (i) Off Board Sensor Systems – Ordo Byantinus Sancti Sepulchri (Byzantine Order of the Holy Sepulchre) – Orbiter Boom Sensor System (space shuttle) – Origins Billion Star Survey
  • OBX – (p) Outer Banks (North Carolina)

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  • OIC – (i) Officer In Charge
  • OIE – (i) World Organisation for Animal Health (originally the Office international des épizooties, French for "International Epizootic Office")
  • OIF – (i) Operation Iraqi Freedom
  • OIOC – (i) Oriental & India Office Collections (in the British Library)

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  1. Historically, as the Irish-language name for the original Irish Republican Army ("Old IRA")
  2. In modern times, as the Irish-language name of the Defence Forces of Ireland
  3. The name of two groups claiming descent from the Old IRA, one a currently inactive splinter group of the Continuity IRA and the other an active splinter group of the Real IRA

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  • OQ - (i) Order Quantity, in inventory management; the quantity of new items to be ordered. Often expressed as a part of OP/OQ (when quantity OP is reached, order OQ new items)

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  • Oy – (p) Osakeyhtiö (Finnish, "stock company")
  • Oyj – (p) Julkinen osakeyhtiö (Finnish, "public stock company")

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  • OZ – Ounce