driver

driver /ˈdraɪvɚ/ noun
plural drivers
driver
/ˈdraɪvɚ/
noun
plural drivers
Britannica Dictionary definition of DRIVER
[count]
1 
a  : a person who drives a car, truck, etc.
— see also backseat driver
b  : a person whose job is to drive a vehicle (such as a taxi, truck, or bus)
2 
technical : a piece of computer software that controls a device (such as a mouse or printer) that is attached to the computer
3 
golf : a club that is used for hitting long shots off a tee

in the driver's seat

: in a position in which you are able to control what happens