- noun a system or piece of equipment of secondary importance
- noun an extra, add-on device, e.g. a mouse or printer, that is attached to or used with a computer
- A device which is not essential for the proper operation of another, but that adds functionality to it.
- A device that adds functionality to a computer. Usually synonymous with peripheral (1).
- noun a person who helps or advises someone who commits a crime
- noun something which helps something else to happen or operate, but may not be very important in itself