If you have searched for the term you are likely looking for more than just a definition. You want a roadmap. Tantra is arguably one of the most misunderstood, misrepresented, and complex spiritual traditions in the world. Spanning over 1,500 years, multiple religions (Hinduism, Buddhism, Jainism), and dozens of languages (Sanskrit, Tibetan, Newari), The Index of Tantra is less a single book and more a living library of esoteric knowledge.
When people search for an "index of tantra" today, they are usually looking for open-access directories containing PDFs of rare Sanskrit texts. These archives often house: Vijnana Bhairava Tantra index of tantra