This list contains acronyms, initialisms, and pseudo-blends that begin with the letter O.
An acronym is an abbreviation pronounced as a series of constituent letters; an initialism is an abbreviation whose pronunciation is wholly or partly the names of constituent letters; and a pseudo-blend is an abbreviation whose extra or omitted letters means that it cannot be considered a true acronym, initialism, or portmanteau (a word formed by combining two or more words).
- (a) = acronym in the example: SARS - (a) Severe acute respiratory syndrome
- (i) = initialism in the example: CD - (i) Compact disc
- (p) = pseudo-blend in the example: UNIFEM - (p) United Nations Development Fund for Women
- (s) = symbol (none of the above, stands for and is read as something else; for example: MHz - Megahertz)
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Please add your own, in a quasi-dictionary order with lowercase treated the same as uppercase and ignoring non-alphanumeric characters (hyphens and such). This means that only alphanumeric characters have any significance in determining order, and that lowercase letters occupy the same ordering position as uppercase (in tie-breaker cases, list lower case first). For example: Algol appears before ALS. (This differs from a strict ASCII ordering.)
- O - (i) Oberst - Observer - Obstacle - Octal - Officer - Official - Oh - Operational - Operator - Oprah (magazine) - Oustanding - (s) Oxygen
OA
OB
- ob - (p) obiit (Latin, "(s)he died")
- OB - (p) Obedience - Obligation - Obligatory - Obsolete - Obstetrics - (i) Ocean Beach (California) - Off Break (cricket) - 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)
- 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
OC
- OCA - (i) Observatoire de la Côte d'Azur - Offensive Counter-Air
- OCOKA - (a) Observation, Cover and concealment, Obstacles, Key terrain, and Avenues of approach (mnemonic)
- OCR - (i) Optical Character Recognition
- OCS - see entry
OD
OE
OF
- OFDA - (i) U.S. AID’s Office of Foreign Disaster Assistance
OG
OH
OI
- OIF - (i) Operation Iraqi Freedom
OJ
OK
- OK - (s) Oklahoma (postal symbol) - (i) oll korrect (facetious alteration of "all correct", 1839)
OL
- OLS - (i) Operational Linescan System
OM
- OM - (s) Oman (ISO 3166 digram)
- OMA - (i) Open Mobile Alliance
- OMB - (i) U.S. Office of Management and Budget - Ontario Municipal Board
- OMN - (s) Oman (ISO 3166 trigram)
- OMNCS (i) U.S. Office of the Manager for the National Communications System
ON
OO
OP
OQ
OR
- OR - (i) Operating Room (surgery) - Operational/Operations Research - (s) Oregon (postal symbol)
- ORF - (i) Operational Readiness Float
- ORR - (i) Office of Refugee Resettlement - (CIA) Office of Research and Reports - Operational Readiness Rate - Operational Readiness Review
OS
OT
- OTB - (p) OneSAF Testbed (the successor to ModSAF )
- OTC - (i) Over-The-Counter (drugs)
- OTEA - (i) (U.S. Army) Operational Test Evaluation Agency
- OTOH - (i) On The Other Hand
OU
OV
- OVC - (s) Overcast (METAR Code)
OW
OX
OY
OZ
See also
