DAB meaning in Military and Defence ?

The Defense Acquisition Board (DAB) is the senior advisory board for defense acquisitions in the Department of Defense of the United States. The board is chaired by the Under Secretary of Defense for Acquisition, Technology and Logistics and includes the Vice Chairman of the Joint Chiefs of Staff, the Service Secretaries (Secretary of the Army, Secretary of the Navy and Secretary of the Air Force), as well as a number of Under Secretaries of Defense. The DAB plays an important role in the Defense Acquisition System. Members of this board are responsible for approving the Major Defense Acquisition Programs (MDAPs) and serve as the most important executive review of expensive acquisition projects that would have potentially large impacts on how wars are fought — things like new tanks, fighter aircraft, or C3 systems.

See DoD Defense Acquisition Guidebook for more information on the process.