Dalai Lama. Buddhism came to Tibet in the 7th c. CE. The Tibetan Buddhist monks are called lamas, a term signifying "one who is superior." Of the three principal orders of monks, the largest is the Gelukpa (often called by Westerners the "Yellow Hats") and the Grand Lama of that order, whose headquarters were at Lhasa, came to be called, in the 16th c., the Dalai Lama. According to tradition, he had gone to Mongolia at the request of a Mongol ruler to revive Buddhism there and was given the title "Dalai", which means "the sea", in allusion to the depth of wisdom he displayed. Until the Chinese communists invaded Tibet in 1950, he was both the spiritual and the temporal ruler of Tibet and widely regarded as an incarnation of the Buddha. When the Tibetans rose in rebellion in 1959, they were ruthlessly quelled and the Dalai Lama and some others made their escape to India.

Geddes MacGregor, Dictionary of Religion and Philosophy, New York: Paragon House, 1989

Dalai Lama

An honorific title derived from Mongolian, the first part of which (dalai) means ‘ocean’. Altan Khan, the Mongol ruler of Kokonor, conferred this title on the early Gelukpa teacher Snam Gyatsho (bsod-nams rgya-mtsho, 1543-88) in 1578. The same title was then applied retrospectively to his two previous incarnations, Gendün Drup (dge-'dun grub) 1391-1474 and Gendün Gyatsho (dge-'dun rgya-mtsho) 1476-1542, who became known respectively as Dalai Lama I and Dalai Lama II. From that time onwards, the successive incarnations through to the current Dalai Lama XIV have all been given this title. From the time of the Dalai Lama V in the mid-18th century, the Dalai Lamas were the titular heads of state in Tibet as well as the spiritual leaders of the Gelukpa. See also Mongolia.

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