backseat driver
noun [ C ] uk/ˌbæk.siːt ˈdraɪ.vər/ us/ˌbæk.siːt ˈdraɪ.vɚ/
乱指点司机的乘客;多管闲事的人
a passenger in a car who keeps giving the driver advice that he or she has not asked for
figurative It is expected that the former CEO will be a backseat driver (= have a controlling influence on what happens) on the company's board. 人们料定前任首席执行官会对董事会指手画脚。