Hard rubber is a durable and tough material that is used for various purposes such as automobile tires, shoe soles, and other industrial applications. There are several synonyms for hard rubber, which include ebonite, vulcanite, and synthetic rubber. Ebonite is a type of hard rubber that is black and shiny, while vulcanite is a hard rubber that is made by heating natural rubber with sulfur. Synthetic rubber, on the other hand, is a man-made material that is used as a substitute for natural rubber. These synonyms for hard rubber are commonly utilized in manufacturing and industrial processes and are characterized by their strength, durability, and resilience.