The term 'stubborn one' can be described by four crossword solutions: CUSS (4 letters), MULE (4 letters), ASS (3 letters), and DIEHARD (7 letters). CUSS is an informal word for a swear word, and is often used to express frustration or anger. A MULE is an animal that is known for its stubbornness and strength. An ASS is another animal, similar to a donkey, that is also known for its stubbornness. Finally, DIEHARD is an adjective that means someone who is very loyal and determined, and will not give up easily. All of these words together describe someone who is very stubborn and unwilling to change their opinion.