The phrase "get course" implies a directive or an instruction to acquire knowledge or skills to achieve a specific goal. Antonyms for "get" could be to lose, give up, surrender, or fail to attain. Synonyms for "course" could be path, direction, trajectory, or route. So, antonyms for "get course" could be to deviate from the path, abandon the direction, miss the trajectory, or veer away from the route. However, if we interpret "course" as a meal, then antonyms for "get course" could be to leave, skip, decline, or refuse the dish.