Antonyms for the term "bush leaguer", which means an incompetent or unskilled person, could include words such as professional, expert, skilled, or proficient. These words describe individuals who have mastered their craft, possess the necessary knowledge, and have the experience to perform well in their chosen field. Contrastingly, bush leaguers lack the essential skills or determination needed to excel in their profession. Other antonyms of the word "bush leaguer" may include experienced, knowledgeable, trained, accomplished, and successful. Overall, these words describe individuals who have gained a significant level of expertise in their respective fields and have achieved a high level of competence.