A member of the crew of a spaceship or other spacecraft that travels beyond Earth's atmosphere, or someone trained to serve that purpose.
An American space traveler, when contrasted against equivalent terms from other countries such as cosmonaut, taikonaut, spationaut, and vyomanaut.
A returnee who frequently flies back and forth between Hong Kong and their adopted home country.
A backup or assistant pilot of an aircraft.
To serve as relief or assistant pilot.