What is a: Sesshin

Sesshin: literally "gathering the mind"

A period of intensive meditation (zazen) in a Zen monastery, or in a western Zen centre.

While the daily routine in the monastery requires the monks to meditate several hours a day, during a sesshin they devote themselves almost exclusively to zazen practice.

During the whole Sesshin everything -short rest breaks, meals, and sometimes short periods of work- is performed with the same mindfulness.
During the sesshin period, the meditation practice is occasionally interrupted by the master giving public talks (teisho) and individual direction in private meetings with a Zen Master.

In modern Buddhist practice in Japan and the West, sesshins are typically one, three, five, or seven days in length. Seven-day sesshins are held several times a year at many Zen centers.