Del ‧ phic or ‧ a ‧ cle, the /ˌdelfɪk ˈɒrək ə l $ -ˈɔː- -ˈɑː-/ BrE AmE
a ↑ temple (=a holy building) in Delphi in ancient Greece where a ↑ priestess gave answers from the god Apollo to questions people asked him. The answer was often in the form of a mysterious ↑ riddle (=a deliberately confusing question with a clever answer) . Someone who is a respected authority on a particular subject is sometimes called a Delphic oracle:
Mrs Thatcher was regarded as the Delphic oracle of modern conservatism.