someone who maintains and audits business accounts
"The new controller will take over all our financial audits next month to ensure every account is accurate."
a person who directs and restrains
"The experienced controller managed to calm the panicked crowd before they reached the stage."
a mechanism that controls the operation of a machine
"the speed controller on his turntable was not working properly"
"I turned the controls over to her"
One who controls something.
"The game controller became unresponsive, leaving me unable to control my character during the final boss fight."
In plain English: A controller is a person who manages or directs how something is done.
"The game controller is too small for my hands to hold comfortably."
Usage: A controller is a person or system that manages, regulates, or directs the operation of a specific machine, process, or organization. Use this term to describe someone with authority over an entity or a device designed to automate control functions.
The word controller comes from the Old French term for a person who checks accounts or rolls. It entered English through Middle English and is related to the word control.