O

o

ohm

O

(Chem.) oxygen

O&M

Operations and Maintenance

o.

octavo, off, old, only, order

O.

Ocean, octavo, Ohio

O. D.

olive drab, overdraft, over drawn

O. P.

observation post

O.A.S.

Organization of America States

O.E.D.

Oxford English Dictionary

O.E.E.C.

Organization for European Economic Cooperation

O.H.M.S.

On Her Majesty’s Service, on His Majesty’s Service

O.I.T.

Office of International Trade

O.M.

order of merit

O.N.I.

Office of Naval Intelligence

O.N.R.

Office of Navel Research

O.T.

occupational therapy, Old Testament, overtime

o/a

on account

o/s

out of stock

OA

Operational Analysis

OAPEC

Organization of Arab Petroleum Exporting Countries

OAS

Offensive Avionics System

OAS

Organization of American States

OASD

Office of the Assistant Secretary of Defense

OASD(HA)

Office of the Assistant to the Secretary of Defense for Health Affairs

OASD/(DR&E)

Office of the Assistant Secretary of Defense (Defense Research & Engineering)

OASD/(SO/LIC)

Office of the Assistant Secretary of Defense (Special Operations/Low Intensity Conflict)

OASIS

Operational Applications of Special Intelligence Systems

OAT

Outside air temperature.

OAU

Organization of African Unity

OB

Order of Battle

ob.

 He or She died, incidentally, obstetric, obstetrics

obdt.

obedient

OBEWS

onboard electronic warfare simulator

obj.

object, objection, objective

obl.

oblique, oblong

OBOGS

Onboard oxygen generating system.

obs

observation

obs.

observation, observatory, obsolete, obstetric,

obstetrics.

obstet.

obstetric, obstetrics

oc.

ocean

OCA

Offensive Counter Air

OCC

Operational Control Center

occas.

occasional, occasionally

OCCIS

Operations Control and Command Information System

OCCULT

Optical Covert Communications Using Laser Transceivers

oceanog.

oceanography

OCP

Observation Command Post

oct.

octavo

Oct.

October

OCU

operational conversion unit(s)

ODA

official development assistance

ODCSLOG

Office of the Deputy Chief of Staff for Logistics

ODCSOPS

Office of the Deputy Chief of Staff for Operations and PI

ODCSPER

Office of the Deputy Chief of Staff for Personnel

OE. or O.E.

Old English

OECD

Organization for Economic Cooperation and Development

OECS

Organization of Eastern Caribbean States

OED

operational evaluation demonstration

OEI

One engine inoperative.

OEM

Original equipment manufacturer

OEU

Operational Evaluation Unit.

OEW

Ordnance and explosive waste

OFC

Overhead foxhole cover

off

official (in Military Balance)

off.

offered, office, officer, official

offic.

official

OFM

Otto Fuel Monitor

OFPP

Office of Procurement and Policy

OGE

Out of ground effect helicopter hovering, far above nearest surface.

OHC

Overhead cam shaft

OHV

Overhead valve

OIC

Organization of the Islamic Conference

OICC

Operational Intelligence Crisis Center

OJCS

Office of the Joint Chiefs of Staff

OKB

missile design bureau (Russia)

Okla.

Oklahoma

OM

operations module

Omega

Long-range hyperbolic radio navaid.

Omen

Ballistic submarine communications project (US)

OMI

Omni-bearing magnetic indicator.

omni

Generalized word meaning equal in all directions (as in omni-range, omni-flash beacon).

Ont.

Ontario

ONUMOZ

see United Nations Operation in Mozambique (UNOMOZ)

ONUSAL

United Nations Observer Mission in El Salvador

OOA

out of area

OOF

other official flows

OOV

objects of verification

OP

observation post/point/position

op.

opera, operation, opposite, out of print

op. cit.

in the work cited.

op/ops

operational /operations

OPAIR

Opposing Air

OPCON

Operational Control

OPCW

Organization for the Prohibition of Chemical Weapons

OPDS

Offshore Petroleum Distribution System

OPEC

Organization of Petroleum Exporting Countries

Opeval

Operational evaluation.

OPLAN

Operation Plan

OPORD

Operation Order

opp.

opposed, opposite

OPSEC

Operational Security

opt.

optical, optician, optics, optional

optronics

Combination of optics and electronics in viewing and sighting systems.

OPV

Offshore Patrol Vessel

OR

operational requirement. Sometimes OR stands for Operational Research, but because of possible confusion with the term Operational Requirement, the term OA is generally used for this subject.

ORATMS

Off-route anti-tank mine system

orch.

orchestra

ord.

order, ordinal, ordinary

Oreg. or Ore.

Oregon

ORF

Operational readiness float

org

organized / organization

org.

organic, organization, organized

orig.

origin, original, originally

orinth.

ornithology

Os,

(Chem.) osmium

OSCAR

Optical Submarine Communications by Aerospace Relay (US)

OSCE

Organization on Security and Cooperation in Europe

OSD

Office of the Secretary of Defense

OSI

Office of Special Investigations (USAF)

OSI

open systems interconnection

OSP

Operational Support Package

OST

Outer Space Treaty

OTC

Officer in Tactical Command

OTH

Over the horizon

OTHB

over-the-horizon backscatter

OTHR

over-the-horizon radar

OTHR/T

over-the-horizon radar / targeting

OTH-SW

over-the-horizon, surface wave

OTPI

On-top position indicator (indicates overhead of submarine in ASW).

OTS

off-the-shelf

OTSG

Office of the Surgeon General

OVE

Onboard vehicle equipment

OWE

Operating weight empty

Oxon.

 Oxford

oz.

ounce, ounces