Synonyms of undiscoverable

2 Syllables
secret, deadpan, mystic
3 Syllables
mysterial, arcane, sphinxlike, difficult, ambiguous
4 Syllables
unknowable, enigmatic, inscrutable, poker-faced, cabalistic, unreadable
5 Syllables
unaccountable, unfathomable, inexplicable, unexplainable, impenetrable
6 Syllables
unintelligible, incomprehensible