Siddhi ("accomplishment/perfection"): spiritual perfection, the attainment of flawless identity with the ultimate Reality (atman or brahman); paranormal ability, of which the yoga tradition knows many kinds
Svarupa-siddhi - the stage in which a bhakta’s svarupa, or internal spiritual form and identity, becomes manifest. This comes at the stage of bhava-bhakti.
Siddhi literally means absolute or total understanding; enlightenment (a state of being "Buddha", also called "Siddha"). Additionally, the word is frequently (Siddhis in plural) used to mean the paranormal powers possessed by saints, mystics, mantriks, and tantriks. The origin is from Sanskrit. [The word is accepted in New English Oxford Dictionary].€€€
The eight supernormal powers or faculties innate in man but at present generally latent or undeveloped, although attainable when a person reaches the status of a buddha.