Synonyms and related words :
able, accepted, believed, credited, enigmatic, incalculable, incognizable, mysterious, puzzling, received, sealed, strange, trusted, unapparent, unapprehended, unascertained, unbeknown, uncharted, unclassified, uncontested, undisclosed, undiscoverable, undiscovered, undisputed, undivulged, undoubted, unexplained, unexplored, unexposed, unfamiliar, unfathomed, unheard, unheard-of, unidentified, uninvestigated, unknowable, unknown, unperceived, unplumbed, unquestioned, unrevealed, untouched, virgin