The term "gussy up" refers to making something more attractive or fancier. However, there are several antonyms that can be used instead of this term, such as "simplify," "unadorn," "plain," "de-glamorize," and "decoy." Rather than gussying up something, one could opt for a more natural and minimalistic approach to enhance its true features. Simplifying or de-glamorizing something can bring out its real essence or beauty. Therefore, instead of gussying up something, it can be a good idea to embrace its simplicity and true nature.