It refers to being struck with the kyosaku (keisaku) literally as "batsu (punishment)" when an unsui (wandering monk) breaks kiku (rules that the unsui should observe).
雲水が、その修行中に規矩（雲水が守るべき規則）を破ってしまった際、文字通り「罰」として警策で打たれることを指す。