DMU means Decision making unit
A DMU is also called a Buying center. In a business environment (B2B) the customer is an organization and a decision to purchase is not by 1 person but by a group of people. This group of people is called the DMU and consists of users, buyers, decision makers and other people who influence the buying process. The composition of the group still wants to change during the whole process, so the salesman will have to respond to this. The more important the product is to buy, the more people are involved in the DMU.