caturmahārāja (Sanskrit; Pāli, catummahārājika). The ‘four great kings’, being four powerful gods (devas) who rule over the lowest of the heavens and thus are close to the human world, which they are said to visit frequently with their retinues. Each king is regent of one of the four cardinal points and they protect the Buddha and his followers in those regions. See also Lokapāla.

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