When we use the phrase "casts about," we typically mean that someone is searching for something or trying to make sense of a situation through a process of trial and error. Antonyms for this phrase might include more definitive or confident actions, such as "decides," "plans," or "executes." These words suggest a clearer sense of purpose and direction, whereas "casts about" can imply a looser, more exploratory approach. Other antonyms might include terms like "forecasts," "predicts," or "assumes," which suggest a more analytical, predictive mindset rather than one which is simply feeling its way through an uncertain situation.