yoga-tantra (Sanskrit). The third class of tantra according to the late standardized classificatory scheme, although during the 8th century ce, tantras later categorized as anuttara-yoga-tantra were also included in this class. In contrast to kriyā-tantra type of practice, yoga-tantra is traditionally said to emphasize internal meditational and yogic practices. Few tantras belonging to this class have survived but most noteworthy is the large Sarva-tathāgata-tattva-saṃgraha which is regarded as the root tantra of the yoga-tantra class.

A Dictionary of Buddhism, Oxford University Press, 2003, 2004 (which is available in electronic version from answer.com)