The word "un-dexterous" refers to someone who is clumsy or awkward. However, there are a number of antonyms (words that mean the opposite) that could be used to describe someone who is skilled, graceful, or agile. Some possible antonyms for "un-dexterous" might include words like "dexterous," "skillful," "nimble," "adept," or "coordinated." These words imply a level of competence or expertise that is absent from the term "un-dexterous." Other antonyms might include more specific terms related to different types of physical ability, such as "athletic," "acrobatic," "fluent," or "graceful.