thermionic

noun Physics.

1. an ion emitted by incandescent material.

adjective

1. of, relating to, or operated by electrons emitted from materials at high temperaturesa thermionic valve

noun

1. physics an electron or ion emitted by a body at high temperature

1. An electrically charged particle or ion that is emitted by a heated conducting material. The electrons emitted from the cathodes of electron tubes (such as cathode ray tubes) are thermions.