Backseat Driver / Armchair Quarterback
A backseat driver is a vehicle passenger who is not
controlling the vehicle and seems to be uncomfortable with the skills of
the driver and/or wants to tutor the driver while the driver is at the
wheel. Some backseat drivers exhibit this type of behavior simply
because they feel unsafe or out of control since they are not driving
the vehicle and therefore are nervous and jumpy and overly eager to give
suggestions and criticism about the driver's actions.
The term is also used allusively, for a person who
gives advice and instructions about what he or she is not responsible
for, and may not well understand.
Armchair quarterback is a related idiom which
refers to a sports fan who seems to know better than the players
themselves and is always eager to shout advice whether he/she be live at
the game or more commonly sitting at home in their chair. (hence
"armchair") This term can be used in many of the same situations as