What is Change Management?

Legal Definition
Change management (CM) refers to any approach to transitioning individuals, teams, and organizations using methods intended to re-direct the use of resources, business process, budget allocations, or other modes of operation that significantly reshape a company or organization. Organizational change management (OCM) considers the full organization and what needs to change. Organizational change management principles and practices include CM as a tool for change focused solely on the individual.

CM focuses on how people and teams are affected by an organizational transition. It deals with many different disciplines, from behavioral and social sciences to information technology and business solutions. In a project management context, CM may refer to the change control process wherein changes to the scope of a project are formally introduced and approved.
-- Wikipedia
Legal Definition
Involving key players and stakeholders in organizational change to minimize resistance.