From: International Federation of Operational Research Societies :
Operational Research can be described as a scientific approach to the solution of problems in the management of complex systems. In a rapidly changing environment an understanding is sought which will facilitate the choice of more effective solutions which, typically, may involve complicated interaction among people, materials, and money.
Operational Research has been used intensively in business, industry, and government. Many new analytical methods have evolved, such as mathematical programming, simulation, game theory, queuing theory, networks, decision analysis, multicriteria analysis, etc. which have powerful application to practical problems with the appropriate logical structure.
Operational Research in practice is a team effort, requiring the close cooperation among the decision-makers, the skilled OR analysts, and the people who will be affected by management action.
From: The Operational Research Society of UK:
Operational Research (OR for short) looks at an organisation's operations - the functions it exists to perform. The objective of operational Researchers is to work with clients to find practical and pragmatic solutions to operational or strategic problems, often working within tight timing constraints. Once a good or better way of proceeding has been identified, Operational Researchers can also be central to the management of implementing the proposed changes.
Organisations may seek a very wide range of operational improvements - for example, greater efficiency, better customer service, higher quality or lower cost. Whatever the business engineering aim, OR can offer the flexibility and adaptability to provide objective help.
Most of the problems OR tackles are messy and complex, often entailing considerable uncertainty. OR can use advanced quantitative methods, modelling, problem structuring, simulation and other analytical techniques to examine assumptions, facilitate an in -depth understanding and decide on practical action.