text: Military Terms
  observed fire — The point of projectile impact or burst that can be seen by an observer, and can be adjusted on
  the basis of observation. (FM 3-09)
  obstacle — (DOD) Any barrier designed or employed to disrupt, fix, turn, or block the movement and maneuver,
  and to impose additional losses in personnel, time, and equipment. (JP 3-15)
  obstacle belt — (DOD) A brigade-level command and control measure, normally depicted graphically, to show
  where within an obstacle zone the ground tactical commander plans to limit friendly obstacle employment and
  focus the defense. (JP 3-15)
  obstacle control measures — Specific measures that grant obstacle-emplacing authority. (FM 3-90)
  obstacle group — One or more individual obstacles that provide a specific obstacle effect. (FM 3-90)
  obstacle line — A conceptual control measure used at battalion or brigade level to show placement intent
  without specifying a particular type of linear obstacle. (FM 1-02.1)
  obstacle restricted areas — (DOD) A command and control measure used to limit the type or number of
  obstacles within an area. (JP 3-15) See also obstacle.
  obstacle zone — (DOD) A division-level command and control measure to designate specific land areas where
  lower echelons are allowed to employ tactical obstacles. (JP 3-15)
  occupy — A tactical mission task in which a unit moves into an area to control it without enemy opposition. (FM
  3-90)
  offensive counterair — (DOD) Offensive operations to destroy or neutralize enemy aircraft, missiles, launch
  platforms, and their supporting structures and systems both before and after launch, and as close to their
  source as possible. (JP 3-01) Also called OCA.
  offensive cyberspace operations — (DOD) Missions intended to project power in and through cyberspace. (JP
  3-12) Also called OCO.
  offensive fires — Surface to surface indirect fires intended to preempt enemy actions in support of the
  maneuver commander’s concept of operations. (FM 3-09)
  offensive operation — An operation to defeat or destroy enemy forces and gain control of terrain, resources,
  and population centers. (ADP 3-0)
  offensive space control — (DOD) Offensive operations conducted for space negation. (JP 3-14) Also called
  OSC.
  official information — Information that is owned by, produced for or by, or is subject to the control of the United
  States government. (FM 3-61)
  offshore petroleum distribution system — A bulk petroleum transfer system used by offshore tankers to
  provide petroleum for storage in the beach support area, or for onward movement inland. (ATP 4-43) Also
  called OPDS.
  on-call target — (DOD) Planned target upon which fires or other actions are determined using deliberate
  targeting and triggered, when detected or located, using dynamic targeting. (JP 3-60)
  on-order mission — A mission to be executed at an unspecified time. (FM 5-0)
  on-scene commander — (DOD) 1. An individual in the immediate vicinity of an isolating event who temporarily
  assumes command of the incident. (JP 3-50) Also called OSC.
  on-station time — (DOD) The time an aircraft can remain on station, which may be determined by endurance or
  orders. (JP 3-50)
  open source — Any person or group that provides information without the expectations of privacy — the
  information, the relationship, or both is not protected against public disclosure. (ATP 2-22.9-1)
  open-source information — (DOD) Information that any member of the public could lawfully obtain by request
  or observation as well as other unclassified information that has limited public distribution or access. (JP 2-0)
  open-source intelligence — (DOD) Relevant information derived from the systematic collection, processing,
  and analysis of publicly available information in response to known or anticipated intelligence requirements.
  (JP 2-0) Also called OSINT.
  operation — (DOD) 1. A sequence of tactical actions with a common purpose or unifying theme. (JP 1 Volume
  1)2. A military action or the carrying out of a strategic, operational, tactical, service, training, or administrative
  military mission. (JP 3-0)
  operation assessment — (DOD) 1. A continuous process that measures the overall effectiveness of employing
  capabilities during military operations to achieve stated objectives.
  2.Determination of the progress toward accomplishing a task, creating an effect, changing a condition, or
  achieving an objective. (JP 5-0)