1.Definition: having a secret or hidden meaning

"Thoroughly sibylline in most of his pronouncements"

Related Adjective(s):cabalistic, cryptic, cryptical, kabbalistic, qabalistic

2.Definition: resembling or characteristic of a prophet or prophecy

"A kind of sibylline book with ready and infallible answers to questions"

Related Adjective(s):divinatory, mantic, sibyllic, vatic, vatical