The term 'Fancy Button' can be summarized as a decorative fastener, usually made of metal or plastic, that is used to secure two pieces of fabric together. The crossword solution for this term is 'STUD', which is a type of button that has a post or pin on the back that is inserted through a hole in the fabric and then secured with a nut or other fastener. STUD buttons are often used in formal wear and are often decorated with jewels or other ornamental designs.