The term 'Tough, Fibrous Tissue' can be summarized as SINEW, which is a five-letter word. SINEW is a type of connective tissue that is composed of strong, fibrous proteins and is found in tendons and ligaments. It is responsible for connecting muscle to bone and providing support and strength to the body. SINEW is also known for its elasticity and durability, making it an important component of the human body.