Odic shield, in magical theory and practice, is a field of etheric energy that protectively surrounds the outer edge of the human aura warding off hostile magic or assaults of spirits. Several methods are used to establish and maintain the odic shield. Related to it is the phenomenon of the shroud of concealment used during rituals of invisibility. A.G.H.
Source:
Greer, John Michael.The New Encyclopedia of the Occult. St. Paul, MN, Llewellyn Worldwide. p. 340