O
ohm     o
(Chem.) oxygen     O
Operations and Maintenance    O&M
octavo, off, old, only, order     o.
Ocean, octavo, Ohio     O.
olive drab, overdraft, over drawn     O. D.
observation post     O. P.
Organization of America States     O.A.S.
Oxford English Dictionary     O.E.D.
Organization for European Economic Cooperation     O.E.E.C.
On Her Majesty’s Service, on His Majesty’s Service     O.H.M.S.
Office of International Trade     O.I.T.
order of merit     O.M.
Office of Naval Intelligence     O.N.I.
Office of Navel Research     O.N.R.
occupational therapy, Old Testament, overtime    O.T.
on account     o/a
out of stock     o/s
Operational Analysis    OA
Organization of Arab Petroleum Exporting Countries    OAPEC
Offensive Avionics System    OAS
Organization of American States    OAS
Office of the Assistant Secretary of Defense    OASD
Office of the Assistant to the Secretary of Defense for Health Affairs    OASD(HA)
Office of the Assistant Secretary of Defense (Defense Research & Engineering)    OASD/(DR&E)
Office of the Assistant Secretary of Defense (Special Operations/Low Intensity Conflict)    OASD/(SO/LIC)
Operational Applications of Special Intelligence Systems    OASIS
Outside air temperature.    OAT
Organization of African Unity    OAU
Order of Battle    OB
 He or She died, incidentally, obstetric, obstetrics     ob.
obedient     obdt.
onboard electronic warfare simulator    OBEWS
object, objection, objective     obj.
oblique, oblong     obl.
Onboard oxygen generating system.    OBOGS
observation    obs
observation, observatory, obsolete, obstetric,
obstetrics.    obs.
obstetric, obstetrics     obstet.
ocean     oc.
Offensive Counter Air    OCA
Operational Control Center    OCC
occasional, occasionally     occas.
Operations Control and Command Information System    OCCIS
Optical Covert Communications Using Laser Transceivers     OCCULT
oceanography    oceanog.
Observation Command Post    OCP
octavo     oct.
October     Oct.
operational conversion unit(s)    OCU
official development assistance    ODA
Office of the Deputy Chief of Staff for Logistics    ODCSLOG
Office of the Deputy Chief of Staff for Operations and PI    ODCSOPS
Office of the Deputy Chief of Staff for Personnel    ODCSPER
Old English     OE. or O.E.
Organization for Economic Cooperation and Development    OECD
Organization of Eastern Caribbean States    OECS
operational evaluation demonstration    OED
One engine inoperative.    OEI
Original equipment manufacturer    OEM
Operational Evaluation Unit.    OEU
Ordnance and explosive waste    OEW
Overhead foxhole cover    OFC
official (in Military Balance)    off
offered, office, officer, official     off.
official     offic.
Otto Fuel Monitor    OFM
Office of Procurement and Policy    OFPP
Out of ground effect helicopter hovering, far above nearest surface.    OGE
Overhead cam shaft    OHC
Overhead valve    OHV
Organization of the Islamic Conference    OIC
Operational Intelligence Crisis Center    OICC
Office of the Joint Chiefs of Staff    OJCS
missile design bureau (Russia)    OKB
Oklahoma     Okla.
operations module    OM
Long-range hyperbolic radio navaid.    Omega
Ballistic submarine communications project (US)    Omen
Omni-bearing magnetic indicator.    OMI
Generalized word meaning equal in all directions (as in omni-range, omni-flash beacon).    omni
Ontario    Ont.
see United Nations Operation in Mozambique (UNOMOZ)    ONUMOZ
United Nations Observer Mission in El Salvador    ONUSAL
out of area    OOA
other official flows    OOF
objects of verification    OOV
observation post/point/position    OP
opera, operation, opposite, out of print     op.
in the work cited.     op. cit.
operational /operations    op/ops
Opposing Air    OPAIR
Operational Control    OPCON
Organization for the Prohibition of Chemical Weapons    OPCW
Offshore Petroleum Distribution System    OPDS
Organization of Petroleum Exporting Countries    OPEC
Operational evaluation.    Opeval
Operation Plan    OPLAN
Operation Order    OPORD
opposed, opposite     opp.
Operational Security    OPSEC
optical, optician, optics, optional     opt.
Combination of optics and electronics in viewing and sighting systems.    optronics
Offshore Patrol Vessel    OPV
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.    OR
Off-route anti-tank mine system    ORATMS
orchestra     orch.
order, ordinal, ordinary     ord.
Oregon     Oreg. or Ore.
Operational readiness float    ORF
organized / organization    org
organic, organization, organized     org.
origin, original, originally     orig.
ornithology     orinth.
(Chem.) osmium     Os,
Optical Submarine Communications by Aerospace Relay (US)    OSCAR
Organization on Security and Cooperation in Europe    OSCE
Office of the Secretary of Defense    OSD
Office of Special Investigations (USAF)    OSI
open systems interconnection    OSI
Operational Support Package    OSP
Outer Space Treaty    OST
Officer in Tactical Command    OTC
Over the horizon    OTH
over-the-horizon backscatter    OTHB
over-the-horizon radar    OTHR
over-the-horizon radar / targeting    OTHR/T
over-the-horizon, surface wave    OTH-SW
On-top position indicator (indicates overhead of submarine in ASW).    OTPI
off-the-shelf    OTS
Office of the Surgeon General    OTSG
Onboard vehicle equipment    OVE
Operating weight empty    OWE
Oxford     Oxon.
ounce, ounces     oz.