- (in combination) A controller, trainer, someone who handles a specified thing, animal or person (especially a prizefighter).
"The spy's handler told him to approach the subject by posing as a dog handler."
- (literally) One who handles something (especially manually) or someone.
"The handler of a weapon gets a symbolic sensation of deadly power."
- (computing) A subroutine that handles a particular situation such as an event or exception.