Cool is a word that is often used to describe something or someone that is fashionable, stylish, or impressive. However, there are times when you might want to describe something that is the opposite of cool. In such cases, you can use antonyms for cool like uncool, boring, dull, old-fashioned, out-of-date, and lame. An uncool thing would not be stylish or fashionable, and would generally be seen as dull or boring. On the other hand, something that is old-fashioned or out-of-date might be seen as obsolete or obsolete. These words are often used to describe a person or object that is not trendy, fashionable, or impressive.