A disk or short cylinder fitting closely within a tube in which it moves up and down against a liquid or gas, used in an internal combustion engine to derive motion, or in a pump to impart motion.
A PWC (Personal Water Craft) is a small pleasure craft that uses an inboard jet drive as its primary source of propulsion and is designed to be operated by a person or persons sitting, standing, [...]
An outboard motor is a propulsion system for boats, consisting of a self-contained unit that includes engine, gearbox, and propeller or jet drive, designed to be affixed to the outside of the transom.