Retreat
a military operation, in which an army retires before an enemy; properly, an orderly march, in which circumstance it differs from a flight.
Also a military signal given in the army by beat of drum or sound of trumpet at sunset, or for retiring from exercise or from action. In Church usage, a period of retirement to a religious religious house, for self-examination, meditation, and prayer.
Retreats commonly last either three or seven days, and are conducted by a cleric, who delivers addresses daily. They are in use both in the Roman and among the High Church party, in the Anglican Church.