Undiscovered things haven't been found yet. You might dream of becoming an explorer and mapping undicovered lands — or you might hope to be a scientist who finds previously undiscovered cures for disease.
Use this adjective for things that have remained unknown or not discovered for a long period of time. Some of these will be undiscovered only to you, like the undiscovered secret garden in your city or a pile of undiscovered postcards your grandparents sent each other. Undiscovered comes from the prefix un-, or "not," and discover, "reveal, uncover, or disclose."