Definitions 
The nature and needs
of organizations are changing dramatically. Correspondingly, the profession of
organization development (OD) has been changing to meet the changing needs of
organizations. Therefore, it may be most useful to consider several definitions
of organization development. 
“Organization Development is an effort planned, organization-wide, and managed from the top, to increase organization effectiveness and health through planned interventions in the organization's 'processes,' using behavioral-science knowledge.” -- Beckhard, “Organization development: Strategies and Models”, Reading, MA: Addison-Wesley, 1969, p. 9.
"OD is a planned process of developing an organization to be more effective in accomplishing its desired goals." Human Resources Management & Development Handbook
"OD is a planned intervention aimed at improving individual and organizational health and effectiveness." Jac Fitz-Enz
"Organization development practitioners help companies manage change and align people, process and practices or success.,, In its simplest form, OD work aims to be a catalyst that helps the organization get from where it is today (point A) to its desired state (Point B)" - ASTD American Society for Training and Development
"Organizational development is a long-term effort led and supported by top management, to improve an organization's visioning, empowerment, learning, and problem-solving processes, through an ongoing, collaborative management of organizational culture-with special emphasis on the consultant-facilitator role and the theory and technology of applied behavioral science, including participant action research." Organization Development, [French & Bell, 1999]
"Organizational development is the application of behavioral scientific principles and methods to increase an organization's effectiveness". US Government Office of Personnel Management
"Organizational development is a management field that focuses on helping organizations to develop their full potential". University of Massachusetts
"Organization Development (OD) is the process of improving organizations". Chicago OD Network
"Organizational development is an effort, planned, organization-wide, and managed from the top, to increase organization effectiveness and health through planned interventions in the organization's processes, using behavioral-science knowledge" Richard F. Beckert
"Organizational Development is the field of study and practice that focuses on various aspects of organizational life, aspects that include culture, values, systems and behavior. The goal of O.D. is to increase organizational effectiveness and organizational health, through planned interventions in the organization’s processes or operations. Most often, O.D. Services are requested when an organization (or a unit within an organization) is undergoing a process of change". University of California
"Our purpose as professionals is to facilitate processes by which human beings and human systems live and work together for their mutual benefit and mutual well-being". The OD Network
“Organization Development is the attempt to influence the members of an organization to expand their candidness with each other about their views of the organization and their experience in it, and to take greater responsibility for their own actions as organization members. The assumption behind OD is that when people pursue both of these objectives simultaneously, they are likely to discover new ways of working together that they experience as more effective for achieving their own and their shared (organizational) goals. And that when this does not happen, such activity helps them to understand why and to make meaningful choices about what to do in light of this understanding.” -- Neilsen, “Becoming an OD Practitioner”, Englewood Cliffs, CA: Prentice-Hall, 1984, pp. 2-3.
"Organization development is a system-wide application of behavioral science knowledge to the planned development and reinforcement of organizational strategies, structures, and processes for improving an organization's effectiveness." -- Cummings and Worley, "Organization Development and Change", Sixth Edition, South-Western Publishing, 1997, p.2.
"Organization Development is a body of knowledge and practice that enhances organizational performance and individual development, viewing the organization as a complex system of systems that exist within a larger system, each of which has its own attributes and degrees of alignment. OD interventions in these systems are inclusive methodologies and approaches to strategic planning, organization design, leadership development, change management, performance management, coaching, diversity, and work/life balance." -- Matt Minahan, MM & Associates, Silver Spring, Maryland
"OD is a field directed at interventions in the processes of human systems (formal and informal groups, organizations, communities, and societies) in order to increase their effectiveness and health using a variety of disciplines, principally applied behavioral sciences. OD requires practitioners to be conscious about the values guiding their practice and focuses on achieving its results through people."- Arnold Minors, Arnold Minors & Associates, Toronto, Canada
Source:
 
