The phrase "most chi chi" refers to something that is fancy, stylish, or high-class. The antonyms for this phrase would be simple, plain, or modest. With these antonyms in mind, it is possible to describe objects, people, or places that are not ostentatious or overly extravagant. Instead, they may be described as understated, unassuming, or humble. The use of these antonyms can help to paint a different picture of the world, one that celebrates the understated beauty and subtle elegance that can be found in many aspects of life.