Design technology, or D.T., is the study, design, development, application, implementation, support and management of computer and non-computer based technologies for the express purpose of communicating product design intent and constructability. Design technology can be applied to the problems encountered in construction, operation and maintenance of a product.
At times there is cross-over between D.T. and Information Technology, whereas I.T. is primarily focused on overall network infrastructure, hardware and software requirements, and implementation, D.T. is specifically focused on supporting, maintaining and training design and engineering applications and tools and working closely with I.T. to provide necessary infrastructure, for the most effective use of these applications and tools. 
Within the building design, construction and maintenance industry (also known as AEC/O/FM), the product is the building and the role of D.T., is the effective application of technologies within all phases and aspects of building process. D.T. processes have adopted Building Information Modeling (BIM) to quicken construction, design and facilities management using technology.  So though D.T. encompasses BIM and Integrated Project Delivery, I.P.D., it is more overarching in its directive and scope and likewise looks for ways to leverage and more effectively utilize C.A.D., Virtual Design & Construction, V.D.C., as well as historical and legacy data and systems.
There are formal courses of study in some countries known as design and technology that focus on particular areas. In this case, the above definition remains valid, if for instance one takes the subject textiles technology and replace the product in the above definition with textile.