a beam of electrons emitted by the cathode of an electrical discharge tube
a stream of electrons, such as that emitted by a heated filament in a tube or emitted by the cathode of a gas-discharge tube when the cathode is bombarder by positive ions.
A negatively charged beam of particles ( electrons) that are emitted from the negative terminal in a vacuum tube.
Cathode rays are streams of electrons observed in vacuum tubes, i.e. evacuated glass tubes that are equipped with at least two electrodes, a cathode (negative electrode) and an anode (positive electrode) in a configuration known as a diode.