Oracle — Definition
Oracle is one of the oldest words in the divinatory vocabulary. In ancient Greece it meant a sanctuary like Delphi where a priestess delivered prophecies; today it most often refers to oracle decks — themed card sets that, unlike tarot, have no fixed structure of suits or arcana. Oracle decks tend to be more direct and message-based than tarot, and many readers use them alongside tarot rather than instead of it.
Origin
From the Latin oraculum, derived from orare, "to speak" or "to pray."
Example
Many readers begin a session by pulling one oracle card to set the tone and then drawing tarot for the structured question.