Greek to one, able, ambiguous, arcane, beyond understanding, cabalistic, enigmatic, impenetrable, inarticulate, incalculable, incognizable, incoherent, incomprehensible, inscrutable, mysterious, mystic, numinous, past comprehension, puzzling, rambling, sealed, strange, unapparent, unapprehended, unascertained, unbeknown, uncharted, unclassified, unconnected, undisclosed, undiscoverable, undiscovered, undivulged, unexplained, unexplored, unexposed, unfamiliar, unfathomable, unfathomed, ungraspable, unguessed, unheard, unheard-of, unidentified, unimaginable, unintelligible, uninvestigated, unknown, unperceived, unplumbed, unrevealed, unsearchable, unsuspected, untouched, virgin