O Ring

Obey

Object

Object Class

Objective

Objective Audit Evidence

Objective Evidence

Object Oriented Analysis (OOA)

Object Oriented Approach or Programming (OOA or OOP)

Obligation

Obligee

Obligor

OBS (Organization Breakdown Structure)

Observation

Observe

Obsolescence

Obsolete

Obstacle

Obvious

Occasion

Occupancy

Occupant

Occupant Vulnerability

Occupation

Occupational Accident

Occupational Disease

Occupational Health Hazard

Occupational Illness

Occupational Incident

Occupational Injury

Occupied Space

Occurrence

Ocean Bottom Cable

Ocean Energy

Ocean Thermal Energy Conversion (OTEC)

Octane (C8H18)

Octane Number or Octane Rating

Octet 

OD (Outside Diameter)

Odorant

Odorisation (Odorization)

Odour (Odor)

OECD (Organization for Economic Cooperation and Development)

OECD Dollar

OEM (Original Equipment Manufacturer)

Off Pattern Well

Off Peak

Offence

Offer

Offer Price

Offgas

Office

Office Automation (OA)

Office Furnishing

Office Furniture

Office Information System (OIS)

Office of Environmental Management (EM)

Office Overhead

Official

Official Language

Official Selling Price (OSP)

Offset

Offshore

Offshore Engineering

Offshore Enterprise

Offshore Geotechnical Engineering

Offshore Platform (or Offshore Drilling Rig)

Offshore Wind Farm

Offshore Work

Offshoring

Offsite

Offsite Facility

Offsite Material Bond

Offtake

(OFGEM) Office of Gas and Electricity Markets

Oganesson (Og)

Ohm (Ω)

Ohm's Law

Oil (Crude Oil)

Oil and Gas Business

Oil Gasification

Oil in Water Emulsion

Oil Mining

Oil Paint

Oil Price Escalation (OPE)

Oil Production Facility

Oil Reserves

Oil Resource

Oil Sand

Oil Shale (or Shale Oil)

Oil Spill

Oil Tanker

Oil Well

Oilfield (or Oil Field)

Oily Water

Olefin

Oleflex

Oleochemicals

Olfactory

Oligomer

Oligopoly

Omnibus Account

On behalf of

On Demand Bond

On Demand Economy

On Peak Energy

On Site Generation

On Stream Factor

One Line Diagram or Single Line Diagram (SLD)

Ongoing Commissioning Process

Online

Online Document Management System

Online Facilitator

Online to Offline (O2O) Commerce

Onshore

Onshore Work

Ontology

Opacity 

OPEC (Organization of the Petroleum Exporting Countries)

OPEC Reference Basket (ORB)

OPEC’s Role

Open Circuit Potential

Open Circuit Voltage

Open Cycle Gas Turbine (OCGT)

Open Ended Question

Open Information Source

Open Loop Control System

Open Loop Geothermal Heat Pump System

Open Season

Open System

Open Time

Operability

Operable Capacity

Operable Utilization Rate

Operate

Operating & Maintenance Manual

Operating Capacity

Operating Cycle

Operating Gas Lift Valve (OGLV)

Operating Instruction

Operating Lease

Operating Pressure

Operating Procedure

Operating Surplus

Operating System (OS)

Operating Time

Operating Utilization Rate

Operation

Operation Readiness

Operational Interruption

Operational Lease

Operational Reliability

Operational Risk

Operations Readiness and Assurance (OR&A)

Operator

OPEX (Operational expenditure)

Opinion

Opinion Survey

Opioid

Opportunity

Opportunity Cost

Opt Out

Optimisation (Optimization)

Optimise (Optimize)

Optimum Mixture

Optimum Module Size

Option

Option Benefit

Oral

Oral Toxicity

Orbit

Orbital

Order

Ordinary

Ordinary Commodity

Ore

Organ

Organic

Organic Chemistry

Organic Compound

Organic Electrode

Organic Farming

Organic Fertilizer

Organic Matter

Organic Solar Cell (OSC)

Organic Solvent

Organisation Identifier

Organisation (Organization)

Organisational Innovation

Organise (Organize)

Organism

Organometallic

Organophosphate

Orientation

Oriented Strand Board (OSB)

Orifice

Orifice Plate

Orifice Valve

Origin

Original

Ornament

Orthographic

OS&D (Overage, Shortage and Damage)

Oscillate

Oscillation

OSHA (Occupational Safety and Health Administration)

OSHA Process Safety Management (OSHA PSM)

Osmium (Os)

Osmosis

Osmotic Pressure

Osteoarthritis

Osteoporosis

OTS (Operator Training Simulator)

Out of Control

Outage

Outbound

Outbreak

Outcome

Outfall

Outgassing

Outlay

Outlet

Outlier

Outlook

Output

Output Decay

Output Gap

Outside Coil

Outsource

Outsourced Manufacturing

Outsourcing

Outworker

Over Coverage

Over Estimate

Over Target Baseline (OTB)

Over Target Schedule (OTS)

Overall Plot Plan

Overall Site Plot Plan

Overcharge

Overediting

Overfunding

Overhang

Overhaul

Overhead (OVHD) Cost

Overlap

Overlap Product

Overlay

Overload

Overmature

Overpressure (or Blast Wave)

Override

Overriding Process Control

Overrun

Overshoot

Oversize

Oversize Load

Overt Fault

Overthrust

Overtime

Overview

Overvoltage

Ovonic

Owe

Owner

Owner's Cost

Owner's Project Requirement

Ownership

OWS (Oily Water Separation)

Oxidant

Oxidation

Oxidation Reduction Potential

Oxidation State

Oxidative Stress

Oxide

Oxidizer

Oxidizing Agent

Oxygen (O2)

Oxygen Demand

Oxygen Scavenger

Oxygenate

Oxygenated Gasoline

Ozonation

Ozone (O3)

Ozone Biofiltration

Ozone Depletion

Ozone Hole

Ozonosphere (or Ozone Layer or Ozone Shield)