1. not revealed 2. not easily apprehended or understood

In The Independent, Christina Oakley Harrington, the proprietor of Treadwells, an occult bookstore in London, singles out a Cornell University Press book for special praise:
The Occult Mind by Chris Lehrich [is] a riveting and serious philosophical re-evaluation of the intellectual history of the occult in the West.”

Pagan Pages

1. not revealed 2. not easily apprehended or understood