dongle
A dongle (pronounced DONG-uhl) is a mechanism for ensuring that only authorized users can copy or use specific software applications, especially very expensive programs. Common mechanisms include a hardware key that plugs into a parallel or serial port on a computer and that a software application accesses for verification before continuing to run; special key diskettes accessed in a similar manner; and registration numbers that are loaded into some form of ROM (read-only memory) at the factory or during system setup.
If more than one application requires a dongle, multiple dongles can be daisy-chained together from the same port. Dongles are not in frequent use partly because enterprises don't like to have a serial or parallel port preempted for this use.
