abracadabra, magical formula used by the Gnostics (see Gnosticism) to invoke the aid of benevolent spirits to ward off disease and affliction. It is supposed to be derived from the abraxas, a word that was engraved on gems and amulets or was variously worn as a protective charm. Handed down through the Middle Ages, the abracadabra gradually lost its occult significance, and its meaning was extended to cover any hocus-pocus.