Antonyms for "mill about" include "orderly," "organized," "systematic," and "controlled." These words imply a sense of structure and direction instead of aimless wandering. Another antonym could be "still," which suggests a lack of movement altogether. In contrast, "mill about" implies a chaotic and disorganized scene. Other antonyms could be "focused," "purposeful," or "directed," all of which imply a clear objective or goal. When used in negative contexts, "mill about" can also suggest laziness or indecisiveness. Choose an antonym that conveys a sense of intentionality and direction, rather than randomness or confusion.