What is Middle Management?

Legal Definition
Middle management is the intermediate management of a hierarchical organization that is subordinate to the executive management and responsible for at least two lower levels of junior staff. Unlike the line management, middle management is considered to be a senior (or semi-executive) management position, with respective salary and a package of benefits. Middle managers' main duty is to implement company strategy in the most efficient way. Their duties include creating effective working environment, administrating the work process, making sure it is compliant with organization's requirements, leading people and reporting to the highest level of management.

Middle management may be reduced in organizations as a result of reorganization. Such changes include downsizing, delayering and outsourcing. The changes may be made in order to reduce costs, as middle management is commonly paid more than junior staff, or the changes may be made to make the organization flatter — empowering the employees and making the organization more innovative and flexible.
-- Wikipedia
Legal Definition
People who serve as project managers in flat organizations or are department heads of accounting, marketing, production or business units, and as such, are this specific type of managers. Middle management constitutes the thickest management layer in a traditional, tall pyramid shaped organization. Middle managers typically have two management levels below them for implementing the top management's policies and plans. They are usually among the first to be slashed in the 'resizing' of a firm.