Kālacakra (Sanskrit: कालचक्र; IAST: Kālacakra; Telugu : కాలచక్ర Tibetan: དུས་ཀྱི་འཁོར་ལོ།; Wylie: us-kyi 'khor-lo) is a Sanskrit term used in Tantric Buddhism that means "time-wheel" or "time-cycles". It refers both to a Tantric deity (Tib. yidam) of Vajrayana Buddhism and to the philosophies and meditation practices contained within the Kalachakra Tantra and its many commentaries. The Kalachakra Tantra is more properly called the Kalachakra Laghutantra, and is said to be an abridged form of an original text, the Kalachakra Mulatantra which is no longer extant. Some Buddhist masters assert that Kalachakra is the most advanced form of Vajrayana practice; it certainly is one of the most complex systems within tantric Buddhism.