Glossary

In our collection you will encounter military terminology and acronyms. Here you can find out what they mean.

O

Officer

O Lt Cr

Ordnance Lieutenant Commander

O Tng Bde

Overseas Training Brigade [First World War AIF Infantry Unit]

O-1

Bird dog, United States Army/United States Air Force observation, single engine aircraft (Vietnam War)

OA

Ordnance Artificer

Objective Area

OAEWO

Operational Area Emergency Works Officer

OAT

Outside Air Temperature

OBD

Ordnance Base Depot

Ordnance Beach Detachment

OBE

Officer of the Order of the British Empire. Officers and Warrant Officer's for valued service in Peace or War

OBJ

Object

obs

Observation

Obstacle

Obsn

Observation (USA)

Obsr

Observer (USA)

OBU

Operational Base Unit (RAAF)

OC

Officer Commanding (First World War)

OCA

Operational Control Authority

OCCABA

Open Circuit Compressed Air Breathing Aparatus

OCE

Officer Conducting Exercises (RAN)

OCLF

Officer Commanding Land Force (Signal Unit)

OCNGA

Officer in Charge of National Guard Affairs (USA)

OCO

Office of Civil Operations (Vietnam War)

OCR

Other Christian Religions

OCS

Officer Cadet School

OCT

Ordnance, Commissariat and Transport

OCTU

Officer Cadets' Training Unit

OCU

Operational conversion unit(s)

OD

Officer of the Day

Ordinary Seaman

Odly

Orderly (USA)

OECD

Organisation for Economic Cooperation and Development

OEE

Open Ended Enlistment (ARA Other Ranks)

OETA

Occupied Enemy Territory Administration

OEW

Office of Economic Warfare, Washington

off

Official

Offr

Officer

Oflag

Offizierlager (German) - Prisoner of war camp for officers

OFM

Ordnance Field Manual (USA)

OFOF

Orders for Opening fire

OFP

Ordnance Field Park (Vietnam War)

OFS

Orange Free State

OFSB

Ordnance Field Service Bulletin (USA)

OG

Officer of the Guard (USA)

OG (RAAF)

Operational Group

OGPU

Osobennoye Gosudarstvennoye Politicheskoye Upravlenie (Special State Political Department, USSR)

OHD

Over the Horizon Radar

OHMS

On His/Her Majesty's Service

OHS

Occupational Health and Safety

OI

Operation Instructions

OIC

Officer in Charge

OIN

Operations and Intelligence

OJT

On the job training

OL

Online Aircraft Establishment

OLAC

Operational level of capability

Oleo

Undercarriage leg (RAAF)

OLLA

Office of Lend Lease Administration (Washington)

OM

Member of the Order of Merit

Organisation and Methods

OMC

Owen Machine Carbine (Owen submachine gun)

OME

Ordnance Mechanical Engineer

OMF

Originating Medical Facility

OMGUS

Office of Military Government for Germany (USA)

ONC

Other Non Christians

ONI

Office of Naval Intelligence (USA)

ONTOS

Self propelled direct fire, anti tank weapon (Vietnam War)

ONUC

United Nations Force in the Congo (Peacekeeping)

ONUCA

United Nations Observer Group in Central America (Peacekeeping)

OO

Operation Order

Ordnance Officer

Orderly Officer

OOA

Out of Area

OOB

Order of Battle

OOV

Objects of Veneration

OOW

Officer of the Watch

Op

Observation Post

Operating

Op Gp HQ

Operation Group, Headquarters (RAAF)

op/s

Operational/operations

OPCON

Operational Control

OPD

Operational Planning Division, War Department General Staff (USA)

OPER

Operational Airfield (RAAF)

OPL

Outpost Line (USA)

OPLAN

Operation Plan

OPORD

Operation Order

Ops

Operations

OPSEC

Operations Security (Vietnam)

OPSO

Operations Officer

OQMG

Office of the Quartermaster General (USA)

OR

Other ranks (gunner, private, driver or sapper)

ORBAT

Order of Battle

ORC

Officer's Reserve Corps (USA)

ORD

Ordnance

ORE

Operational Readiness Evaluation (RAN)

org

Operational Research Group

Organised/organisation

ORO

Operations Research Officer (USA)

ORP

Operational Readiness Platform

ORTH

Greek Orthodox

OS

Officer Steward

Orderly Sergeant

Offensive Support (RAN)

OSC

On Scene Commander

OSE

Officer Scheduling Exercises (RAN)

OSGAP

Office of Secretary General in Afghanistan and Pakistan

OSS

Office of Strategic Services (USA)

OSU

Operational Support Unit, RAAF (Vietnam War)

OSW

Office of Secretary of War (USA)

Otago MR Regt

Otago Mounted Rifles Regiment [First World War New Zearland Unit]

OTB

Overseas Training Brigade (First World War)

OTC

Officers' Training Corps

Officer in Tactical Command

OTCI

Overseas Telecommunications Corporation International

OTH

Over the horizon

OTHR

Over the horizon radar

OTHT

Over the horizon targeting

OTS

Officer's Training School

OTT

One Time Tape

OTU

Operational Training Unit (RAAF)

OUSW

Office Under Secretary of War (USA)

OV-1

Mohawk - United States observation aircraft (Vietnam War)

OW

Order Wire

OWI

Office of War Information (USA)

Oxf Bucks

The Oxfordshire and Buckinghamshire Light Infantry

OXY

Oxygen