Mahavairochana Buddha. The Buddha of great light. The dharmakaya (body of the dharma) Buddha who is the central object of worship and focus of meditation of the Shingon Buddhist sect. From at least the eleventh century Amaterasu and Toyo-uke were identified as a manifestation of Dainichi under the auspices of ryobu shinto and the honji-suijaku theory, according to which the inner and outer shrines of Ise jingu were a manifestation of the dual aspects of Dainichi.
A Popular Dictionary of Shinto. Brian Bocking.