The term 'strong coat fabric' can be summarized by the crossword solution 'serge'. Serge is a type of twill fabric that is strong and durable, making it an ideal choice for coats. It is usually made from wool, cotton, or synthetic fibers, and is characterized by its diagonal ribbing. Serge is also known for its ability to resist wrinkles and fading, making it a popular choice for both casual and formal wear.