noun
head priest of a temple
A title for the chief priest of a Buddhist temple, especially in Tendai and other sects. Not a general term for any priest.
延暦寺の座主は天台宗の最高位です。
The head priest of Enryaku-ji is the highest position in the Tendai sect.
住職 is the general term for a temple's chief priest, while 座主 is a specific title used in certain sects for the head of a major temple or the sect itself.
From 座 (seat, position) and 主 (master, head), literally 'master of the seat'. The exact historical derivation is uncertain; the term is a traditional Buddhist title.