Refers to a jet engine, jet aircraft, or a jet of fluid. Common in compounds like ジェット機 (jet plane) and ジェットコースター (roller coaster).
That jet is very fast.
Water gushed out of the faucet like a jet.
jet airplane; jet aircraft
inkjet
roller coaster
whirlpool bath; jacuzzi; jet bath spa
jet lag
Borrowed from English 'jet'.