The term "bung up" has various synonyms that express the same meaning, such as block, obstruct, clog, jam, or impede. However, finding antonyms for this phrase may seem challenging, mainly because it's a phrasal verb that describes an action that usually entails blocking or clogging up something. However, few antonyms for "bung up" can include clearing, freeing, releasing, or opening. These words denote to take away an obstacle or barrier that previously existed. In other words, they express the opposite of "bung up" as they mean to unblock or unhinge something that was clogged or obstructed previously.