Decking out is a term usually associated with dressing up or decorating. Its antonyms can range from casual to plain, and any other terms that indicate the opposite of dressing up or bedecking. Some examples of antonyms for decking out include: dressing down, underdressed, disheveled, plain, simplistic, unpainted, undersupplied, unequipped, or under-adorned. These words suggest either a lack of effort in dressing up or a preference for simplicity over extravagance. While decking out can be a fun way to express oneself, sometimes a more low-key approach is preferable, and we have plenty of words to describe that too.