The Navy Department Library
U.S. Naval Abbreviations
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--O--
Note: Where the same abbreviation has more than one meaning, the several meanings have been arranged alphabetically. Abbreviations preceded by an asterisk (*), other than Navy numbers, may never be used singly; those preceded by the symbol for number (#) are the Bureau of Personnel Condensation Code for use in dispatch orders to personnel.
O -- First letter in the Navy aircraft designation, indicating an observation plane
O -- Horizontal Opposed (aircraft engine)
O -- Lockheed Aircraft Corporation (manufacturer's symbol)
O -- Officer of Operations (USCG)
O -- Organized Naval Reserve
O1 -- Organized Naval Reserve Seagoing
O2 -- Organized Naval Reserve Aviation
OAA -- Radar Test Equipment
OAD -- Officers' Accounts Division
O&A Date -- Oath and Acceptance Date
OAM -- Orthopedic Appliance Mechanic
OAN -- Aids to Navigation Division (USCG)
OANDOS -- Ordnance and Ordnance Stores (USCG)
OAP -- Observation amphibian plane (USCG)
OAS -- Occupied Areas Section (Military Government)
OATC -- Oceanic Air Traffic Center
OATC -- Overseas Air Traffic Control
OAV -- Aviation Division (USCG)
OB -- Operating Base
OB -- Operational Base
OB -- Ordnance Battalion
OB -- Ordnance Board
OBB -- Old Battleship
OBJ -- Radar training device
Oboe -- "O" in the phonetic alphabet
OBR -- Office of Budget and Reports
*OBS -- Observatory
ObsRon -- Observation Squadron
OBSY -- Observatory
OC -- Communications Division (USCG)
OC -- Office of Censorship
OC -- Officer Candidate (Army)
OC -- Officer Commanding (USMC)
O/C -- Officer-in-Charge (Army)
OCAS -- Officer-in-Charge of Armament Supply
Occ -- Occulting
OCD -- Officer of Civilian Defense
OCE -- Officer Conducting the Exercise
OCJ -- Radar Training Device
OCL -- Old Light Cruiser
OCL -- Ordnance Circular Letters
OCNPR -- Operation and Conservation of Naval Petroleum Reserves (appropriation title)
OCR -- Office of Civilian Requirements (WPB)
OCS -- Office of Contract Settlement
OCS -- Officer Candidate School (Army)
OCSigO -- Office of the Chief Signal Officer (Army)
OCT -- Office of the Chief of Transportation (Army)
OCV -- Old Aircraft Carrier
OD -- Officer-of-the-Day
OD -- Ordnance Data (inspection and test data)
ODD -- Old Destroyer
ODP -- Organized Reservists in drill pay status
ODT -- Office of Defense Transportation
OEG -- Operations Evaluation Group
OEM -- Officer of Emergency management
OEW -- Office of Economic Warfare
*OF -- Office(r)
OFEA -- Office of Foreign Economic (Lend-Lease) Administration
OFEC -- Office of Foreign Economic Coordination
OFERRA -- Office of Foreign Economic Relief and Rehabilitation Administration
Off -- Office(r)
OffNavHist -- Office of Naval History
OFLC -- Office of Foreign liquidation Commission
OFP -- Operating Force Plan
OFRR -- Office of Foreign Relief and Rehabilitation
OFRRO -- Office of Foreign Relief and Rehabilitation Operations
OFS -- Office of Field Service (OSRD)
OFT -- Operational Flight Trainer
OFU -- Floating Units Division (USCG)
OG -- Officer of the Guard (Army)
OGC -- Office of General Counsel
OGR -- Ordnance, Gunnery and Readiness Division (USCG)
OGU -- Outgoing Unit
OHI -- Ordnance Handling Instructions
OIAA -- Office of Inter-American Affairs
OIC -- Officer-in-Charge
OIL -- Ordnance Investigation Laboratory
OinC or OINC -- Officer-in-Charge
OinCABCCTC -- Officer-in-Charge, Advanced Base Combat Communication Training Center (Pearl Harbor)
OIR -- Office of Industrial Relations (previously SECP)
"Oka" -- Japanese rocket-propelled one man guided missile; also called "Cherry Blossom"
OKLA -- Oklahoma
OLLA -- Office of Lend-Lease Administration
OLP -- Observation landplane (USCG)
OLP -- Office of Labor Production (WPB)
O&LS -- Ocean and Lake Surveys (Navy) (appropriation title)
OM -- Officer Messenger
OM -- Order of Merit
OME -- Office of Management Engineer
OMGUS -- Office of Military Government United States
OMI -- Ordnance Modifications Instructions
OMM -- Officer Messenger Mail
OMMC -- Officer Messenger Mail Center
OMM(S)C -- Officer Messenger Mail (Sub) Center
OMPUS -- Official Munitions Production United States
ON -- Liverpool to New York, fast (routing designation)
#ONBOSUB -- And on board a submarine of that (fleet, force, squadron, or division, as appropriate)
#ONBOWOOM -- For duty on board that vessel when placed in commission
#ONBOWSERV -- For duty on board that vessel when placed in service
ONH -- Office of Naval History
ONI -- Office of Naval Intelligence
ONM -- Liverpool to New York, medium (routing designation)
ONOP -- Office of Naval Officer Procurement
*ONOP -- Officer-in-Charge, Branch Office of Naval Officer Procurement
ONR -- Office of naval Research (formerly Office of Research and Inventions) (ORI))
ONS -- Liverpool to Halifax, slow (routing designation)
OOD -- Officer-of-the-Deck
O&OS -- Ordnance and Ordnance Stores, Navy (appropriation title)
OP -- Observation post (USMC)
OP -- Office of Chief of Naval Operations
Op 1 (2, etc.) -- Division 1 (2, etc.) of Office of CNO
*OP -- Operating; Operator; Operation(al)
OP -- Operational Priority
OP -- Ordnance Pamphlets
OP -- Ordnance Personnel
OPA -- Office of Price Administration
OpAttyGen -- Opinion of the Attorney General
OPC -- Optician
Op-Com -- Operations-Communications
OPD -- Operations Division (War Department, General Staff)
OpDevFor -- Operations Development Forces
Oper -- Operator
Opers -- Operations
OPET -- Organization, Personnel Equipment and Training (Group)
OP&I -- Office of Patents and Inventions
OpIntel -- Operational Intelligence
OPL -- Outpost Line (Army)
OPLR -- Outpost Line of Resistance (Army)
OP&M -- Office of Procurement and Material
OPM -- Office of Production Management
OPM -- Optometrist
OPMG -- Office of Provost Marshal General (also PMGO)
OpNav -- Office of the Chief of Naval Operations; short title: CNO
OP Plan -- Operating Plan
OPR -- Office of Public Relations
Opr -- Operator
OPS -- Operations
Op(s)ArmyJAG -- Opinion(s) of the Army Judge Advocate General
OPT -- Optician
OpTra -- Air Operational Training
OPU -- Overseas Plexiglass Unit
OQMG -- Office of the Quartermaster General (Army)
OR -- Operations Room
OR -- Orange, Texas
ORA -- Organization de Resistance de L'Armée (France)
Orange -- War plans for use in war against Japan
ORC -- Officers' Reserve Corps (Army)
ORD -- Office of Rubber Director (WPB)
Ord -- Orderly
*ORD -- Ordnance
ORDALT -- Ordnance Alterations
ORDC -- Ordnance Research and Development Center (Aberdeen Proving Grounds, Maryland)
#ORDCAN -- Orders (identified by date or dispatch reference numbers following) are hereby cancelled
#ORDCOR -- Orders (identified by date or dispatch reference numbers following) are hereby corrected
ORD DIS -- Ordinary Discharge
Ord Eng -- Ordnance Engineering
#ORDMOD -- Orders (identified by date or dispatch reference numbers following) are hereby modified
ORE -- Oregon
ORG -- Operations Research Group
ORI -- Office of Research and Inventions; now, Office of Naval Research ONR
Orig -- Original
ORIG -- Originator
ORT -- Operating Room Technician
OS -- First two letters in the Navy aircraft designation, indicating an observation-scouting plane
OS -- Ordnance Specifications
Osc -- Oscillator
OSC -- Own ship's course
OS&D or OS/D -- Over, Short, and Damaged (Report) (Army)
OSFCW -- Office of Solid Fuels Coordinator
OSigO -- Office of Chief Signal Officer
OS2N -- "Kingfisher"; single-engine Navy scout-observation (VSO), seaplane, manufactured by Naval Aircraft Factory
OSRD -- Office of Scientific Research and Development
OSS -- Office of Strategic Services; now, SSU
OSS -- Old Submarine
OSTD -- Ordnance Standards
OSU -- Shore Units Division (USCG)
OS2U -- "Kingfisher"; single-engine Navy scout-observation (VSO), landplane and seaplane, manufactured by Vought-Sikorsky
OSW -- Office of Secretary of War
OT -- Aruba or Curaçoa to Northwest Africa (routing designation)
OT -- Curaçoa to Trinidad (routing designation)
OT -- New York to Netherlands West Indies (routing designation)
OT -- Occupational Therapy Technician
OTC -- Officer-in-Tactical Command
OTC -- Officers' Training School
OTCLant -- Fleet Operational Training Command, Atlantic (usually COTCLant)
OTCPac -- Fleet Operational Training Command, Pacific (usually COTCPac)
OTI -- Ordnance Technical Instructions
OTU -- Operational Training Unit
OUSW -- Office of the Under Secretary of War
OVPD -- Overpaid
O-V(RS) -- USNR designation for ordnance officers, commissioned and warrant, including radio electricians, qualified for specialist duties. This classification was abolished in September 1944 and replaced by the proper aviation or engineering classification with the suffix "T".
O-V(S) -- USNR designation for ordnance officers, commissioned and warrant, including gunners and torpedomen, qualified for specialist duties. This classification was abolished in September 1944 and replaced by one of the following: (D), (D)L, (S), S(O), or S(O) with proper numeral indicating particular specialty within ordnance.
OWI -- Office of War Information
OWM -- Office of War Mobilization
OWM&R -- Office of War Mobilization and Reconversion
OWU -- Office of War Utilities (WPB)
OY-# -- "Sentinel"; observation-scout (VOS), manufactured by Consolidated-Vultee
