The word "unfashionableness" refers to something that is out of trend or not stylish. Its antonyms are words that describe the opposite which is something that is fashionable, stylish, or up-to-date. Synonyms for unfashionableness can include antiquated, outdated, or old-fashioned, but antonyms would include trendy, modern, fashionable, and chic. Other antonyms could include vogue, modish, popular, and contemporary. By using these antonyms, one can express the opposite of unfashionableness and describe something that is currently in trend or popular amongst their peers. It is important to use antonyms to effectively communicate the desired message and to avoid confusion.