What is the meaning of Actuator?

Something that actuates something else.

A usually electric device that causes a mechanical device (i.e., a mechanism) to be switched on or off. For example; an electric motor that opens and closes a valve.

The mechanism that moves the head assembly on a disk drive.

A relay that controls the flow of electricity.

second/third-person singular future passive imperative of āctuō

Source: wiktionary.org