adjective
also syb·il·line ˈsibəˌlīn, -ˌlēn, -_lə̇n
Etymology: Latin sibyllinus, from Sibylla sibyl + -inus -ine
1. often capitalized
a. : of, relating to, resembling, or characteristic of a sibyl : prophetic
the novelist … growing a little sibylline in her success — Lionel Trilling
b. : uttered or written in or as if in prophecy
a kind of Sibylline book in which ready and infallible answers will be found to problems — Times Literary Supplement
2.
a. : mysterious , cryptic , occult
thoroughly sibylline in most of his pronouncements — John Gunther
b. : ambiguous , equivocal
utterances remained sibylline — A.R.E.Pinchot