Definition: The word 'A.U.' refers to a type of material used in construction that provides excellent strength-to-weight ratio, low expansion at room temperature, good thermal shock resistance, high stiffness, and light weight. It is commonly used in building structures due to its lightweight, strong and durable characteristics. A U shaped plate is one example of this type of A.U. This is a common material used in the construction industry due to its ability to provide good strength-to-weight ratio, low expansion at room temperature, good thermal shock resistance, high stiffness, and light weight. It's important to note that A.U. can be compared to other materials such as steel, iron, and concrete as they have similar properties and are used in many construction projects worldwide.