Waterproof cover is a term used to describe a type of material that is designed to protect items from water damage. Two common examples of waterproof cover are oilcloth, which is an 8-letter word, and tarp, which is a 4-letter word. Oilcloth is a heavy cotton fabric that has been treated with oil or wax to make it waterproof. Tarps are made of plastic or canvas and are often used to cover outdoor items such as boats, furniture, and grills.