Antonyms for "busts out" could potentially depend on the context in which the phrase is being used. If it is referring to someone breaking out of prison, possible antonyms could include "stays in," "remains confined," or "obeys the law." Alternatively, if "busts out" is being used in a more celebratory sense, antonyms could include "stays home," "remains low-key," or "avoids attention." In any case, antonyms for "busts out" generally connote remaining in place rather than taking action, and avoiding risk or excitement rather than embracing it.