Sibyl means "prophetess" in Greek, from the Greek word σίβυλλα (sibylla).
It refers most often to the Sibylline books. The Sibylline Books are not the same as the Sibylline Oracles. The Roman Sibylline Books were quite different in character from the preserved Sibylline Oracles, which typically predict disasters rather than prescribe solutions. Some genuine Sibylline verses are preserved in the Book of Marvels of Phlegon of Tralles (2nd century CE).