The term "un-detectable" refers to something that cannot be detected or discerned. Its antonyms, on the other hand, are words that describe things that can be easily noticed or observed. Some common antonyms for "un-detectable" include observable, detectable, visible, noticeable, apparent, and evident. These words all suggest the presence of something that can be easily identified or recognized. If something is undetectable, it may not be seen or felt, whereas if something is observable, it can be seen with the naked eye or other tools. In summary, understanding antonyms for a word like "un-detectable" can help us appreciate its opposite meanings better.