What is "monshu"

The Monshu , or keeper of the gate is a term sometimes used in Japanese Buddhism to denote the head of a monastery, as in the case of Jōdo-shū and Tendai Buddhism, but in the case of the Nishi Hongan-ji sub-sect of Jōdo Shinshū Buddhism, it refers to the spiritual leader of the sect, and direct descendant of its founder Shinran.