Collins Russian Dictionary 2nd Edition © HarperCollins Publishers 2000, 1997:
undiscovered [ˈʌndɪsˈkʌvəd] adj (island) неоткры́тый; (fact) необнару́женный; (situation) неиссле́дованный
* is used to mark translations which have irregular inflections. The Russian-English side of the dictionary gives inflectional information.