The word "un-traditional" suggests something that deviates from established customs, practices, or beliefs. Therefore, its antonyms would be words that suggest adherence to tradition, conventionality, or conformity. Some of these antonyms could be traditional, conventional, customary, orthodox, or established. They convey the idea of following conventional norms or conforming to well-established practices or beliefs. On the other hand, nonconformist or unconventional could be antonyms to "un-traditional" as they suggest a deviation from established norms or expectations. Other potential antonyms include conservative, traditionalist, old-fashioned, classic or time-honored, depending on the context in which the word is used.