The term 'A WATERPROOF RAINCOAT' can be summarized by the three-letter acronym MAC. A MAC is a type of raincoat that is designed to be waterproof, meaning it is able to repel water and keep the wearer dry. It is typically made from a synthetic material such as nylon or polyester, and is often lined with a waterproof membrane to further protect against moisture. The coat usually has a hood and pockets, and may also feature a drawstring waist for added protection.