Untrained means not having received instruction, practice, or preparation for a particular skill or activity. An untrained dog hasn't learned commands like “sit” or “stay.” An untrained singer might have natural talent but hasn't studied proper breathing techniques or how to read music.

The word often highlights what someone lacks compared to those who have learned systematically. An untrained eye might miss details that an expert notices immediately: a doctor spots symptoms an untrained person would overlook, or an art expert identifies a forgery that looks perfect to untrained observers.

Being untrained isn't the same as being incapable. It simply means you haven't developed that specific skill yet. Everyone starts untrained at everything: Olympic gymnasts were once untrained kids learning their first cartwheel, and skilled carpenters were once untrained beginners learning to hammer a nail straight. The opposite of untrained is trained, skilled, or expert. When you practice something consistently and learn from teachers or mentors, you move from untrained to trained.