"Most astir" refers to a state of excitement or commotion. In antonym, we can say "least astir" which means a state of calmness, tranquility, or inactivity. Another antonym is "unexcited", meaning no strong emotions are felt and things are proceeding calmly. Other antonyms for "most astir" may include "dull", "boring", or "quiet", indicating a lack of excitement or activity. It's essential to note that antonyms play an important role in communication because understanding them helps us to describe the opposite state of a particular situation, as well as appreciate the beauty of the language.