Zen. A form of Buddhism. "Zen" is a Japanese rendering of the Chinese Ch'an', meaning "meditation." This school developed as a reaction to classical forms of Buddhism. Originating in India it was brought by Bodhidharma ( 460-534) to China. It has been especially influential in Japan and has become popular in the West. Typical among Zen teaching is the notion that since the Buddha-nature is in all men and the Buddha-mind is everywhere, satori (enlightenment) can be achieved at any time by anyone in any ordinary situation in human life. It is not to be achieved either by asceticism or by thought but by techniques that carry the seeker to a level below (and therefore independent of) intellectual and moral activity.

The koan is used as a jolt, to arrest the mind and the will, wrenching them from their customary bondage and eventually bringing about the seeker's enlightenment. A well-known and characteristic example of the koan is the Zen master's injunction to think of the sound made by one hand clapping. Zazen, which includes yogic techniques, is used to help the seeker to attain the needed detachment for the "solution" of the koan. (See Koan.) Counterparts of the central notions of Zen abound in Christian mystical literature and also in some forms of Western philosophy and literature, for instance, in Croce's concept of the "purity" of the "aesthetic moment" and in the "epiphanies" of James Joyce. The notion that detachment from the habitual categories of thought is necessary for the continued vivacity of thought itself is familiar in Christian existentialism, notably in Kierkegaard, which has antecedents, if not exemplars, in Pascal and other Christian thinkers.

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

Zen

The Japanese pronunciation of the Chinese word ‘Ch'an’, meaning ‘meditation’. This word stands not only for a particular religious technique, but is an umbrella term for the various schools of zen in Japan: Rinzai, Sōtō, Ōbaku, and Fuke. Besides specific reference to the above-named Japanese schools (and their American and European derivatives), the term is also used to cover the entire tradition from which Japanese Zen arose in China, and all of the other derivatives of Ch'an in other countries such as Sŏn in Korea.

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