Adhocracy means that the different parts of an organization are temporarily assembled to meet the requirements and needs which apply at any particular point in time. […] [Henry] Mintzberg considers that adhocracy is characterized by an organic structure, a low degree of formalization, a high degree of horizontal work specialization based on formal training and specialist competence, a tendency to group specialized personnel in functional units to facilitate administration and personal development ("housekeeping purposes"), while employing them in small, market-based project groups in work organizations.
Source: wiktionary