cathode ray

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.When the cathode is heated, it emits radiation which travels to the anode. If the inner glass walls behind the anode are coated with a phosphorescent material, they glow. A metal shape placed between the electrodes casts a shadow on the glowing coating. This suggests that the cause of the light emission was composed of rays emitted by the cathode and hitting the coating. They travel towards the anode in straight lines and continue past it for some distance.
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Cath·ode ray n. 1. A stream of electrons emitted by the cathode in electrical discharge tubes. 2. One of the electrons that is emitted in a stream [more]Cathode ray - Community and Resources

Noun
1. a beam of electrons emitted by the cathode of an electrical discharge tube
(hypernym) beam, ray, electron beam

 Say it 
A negatively charged beam that emanates from the cathode of a discharge tube. Cathode rays are streams of electrons.

Synonyms and related words:
Becquerel ray, Grenz ray, Roentgen ray, X radiation, X ray, actinic ray, alpha radiation, alpha ray, anode ray, beta radiation, beta ray, canal ray, cathode glow, collision emission, cosmic radiation, cosmic ray, cosmic ray bombardment, electron beam, electron emission, electron ray, field emission, gamma radiation, gamma ray, glow discharge, grid emission, infraroentgen ray, nuclear rays, photoemission, positive ray, radiorays, secondary emission, thermionic emission, thermionic grid emission