Hesychasm (Greek: ἡσυχασμός, hesychasmos, from ἡσυχία, hesychia, "stillness, rest, quiet, silence") is an eremitic tradition of prayer in the Eastern Orthodox Church and Eastern Catholic Churches of Byzantine Rite practised (Gk: ἡσυχάζω, hesychazo: "to keep stillness") by the Hesychast (Gr. Ἡσυχαστής, hesychastes).
Based on Christ's injunction in the Gospel of Matthew to "go into your closet to pray", hesychasm in tradition has been the process of retiring inward by ceasing to register the senses, in order to achieve an experiential knowledge of God (see theoria).
Read more about Hesychasm: Meanings of The Term, History of The Term, Hesychastic Practice, Hesychast Controversy, Proposed Biblical and Jewish Origins