Un-prepossessing is a term that refers to something that is unimpressive or unattractive. It is often used to describe people, places, or things that lack the qualities needed to impress or attract others. Some antonyms for un-prepossessing include attractive, charming, impressive, pleasing, appealing, beautiful, gorgeous, elegant, and stunning. These words refer to qualities that make people or things appealing or attractive to others. An attractive person may have a charismatic personality, a great sense of humor, or an exceptional appearance. Similarly, an attractive place or thing may have a beautiful location, a stunning view, or a unique design.