The term "un-decorated" refers to something that lacks ornaments or embellishments. Its opposite is "decorated," which implies the presence of adornments and decorations. Some antonyms for un-decorated could include terms such as embellished, adorned, ornamented, decorated, festooned, bedecked, enlivened, enhanced, and beautified. These antonyms are useful to describe objects or settings that have been adorned with decorative items or details, such as a beautifully decorated Christmas tree or a room filled with colorful embellishments. Using antonyms for un-decorated can help to add variety and depth to our language and convey a more precise image of what we are trying to describe.