Satori is the Japanese word for awakening or understanding, used in Zen for a direct insight into the nature of oneself and of reality. It comes from the verb satoru, to know or to realize.
Zen writing often describes satori as sudden, but it is not regarded as an end point. A first insight may be shallow, and the tradition stresses deepening it through continued practice and bringing it into everyday life.
Teachers tend to discourage chasing the experience. A common instruction is to practice wholeheartedly and leave awakening to look after itself.