Untrained means lack of training or experience in a particular field or task. In contrast, an antonym for untrained would be trained, skilled, experienced, knowledgeable, competent or proficient. A trained individual possesses the necessary skills and knowledge required to carry out a given task effectively. They have had proper instruction and have practiced their skills to make them proficient in their chosen field. Skilled workers have undergone training or an apprenticeship program to gain expertise and become experienced in their job. Proficient individuals have achieved a level of mastery in their field, and they can perform their duties with ease and skillfully. So, the opposite of untrained is skilled, experienced, and proficient.