Back in ancient times, an oracle was someone who offered advice or a prophecy thought to have come directly from a divine source. In modern usage, any good source of information can be called an oracle.
In his Apology, Plato claims that the oracle at Delphi played a vital role in the career of the philosopher Socrates, and a Delphic prophecy sets the tragedy of Sophocles' Oedipus Rex in motion. The word oracle can also be used to describe the utterances of a seer or anyone else who is pretty darn good at predicting the future.
