The word "un-discovered" can be difficult to find antonyms for, as it is a negative word that describes something that has not yet been discovered. However, some possible antonyms for "un-discovered" could include "known," "explored," "charted," "mapped," or "familiar." These words all convey the opposite meaning of "un-discovered," indicating that the subject in question has been found or explored. Additionally, synonyms such as "found" or "discovered" could also be considered antonyms, as they describe the opposite action of the original word. Overall, while there may not be many direct antonyms for "un-discovered," there are several words that can be used to convey its opposite meaning.