1. A rocket that is accelerated by means of a plasma engine or an electrical-reaction engine in which magnetically accelerated plasma is used as the propellant.
2. An engine for space travel in which neutral plasma is accelerated and directed by external magnetic fields that interact with the magnetic field produced by electric current flow through the plasma.

The term plasma in these definitions refers to a gas-like state of matter consisting of positively charged ions, free electrons, and neutral particles.

Plasma is found in the stars, the sun, the solar wind, in lightning, and in fire.