When we say "bundle up," it means we are getting dressed in warm, protective layers. However, there are certain antonyms or opposite words for "bundle up," which mean to dress lightly or uncover. Among these antonyms are strip off, uncover, undress, and de-layer. These words signify the opposite of layering up for warmth. You could use any of them when you refer to removing extra clothes or revealing more skin. Often, people use these antonyms when talking about summer clothing, where light, breezy outfits are favored over thick layers of clothing.