Antonyms for "gussying up" may include terms such as dressing down, simplifying, or disheveling. When we use the term "gussying up," we refer to putting on a fancy outfit, doing our hair and makeup and doing everything to look our best. On the other hand, going for a simpler look may involve wearing comfortable clothing, putting less effort into our hair or makeup, and foregoing fancy accessories. Disheveling, meanwhile, suggests a messy, unkempt appearance. So, while "gussying up" may involve investing lots of time and energy into our appearance, its antonyms suggest a more laid-back, effortless approach.