a back-seat driver

a back-seat driver

COMMON
1. If you call a passenger in a car a back-seat driver, you mean that they keep telling the driver what to do. My mother is a terrible back-seat driver, especially when my sister is at the wheel.
2. If you call someone, especially a politician, a back-seat driver, you mean that they are trying to influence or control a situation that should be controlled by someone else. They accused the former prime minister of being a backseat driver. Note: This expression is used to show disapproval.
See also: driver