(military) A thermonuclear weapon.

(physics) The electromagnetic radiation emitted from a body as a consequence of its temperature; increasing the temperature of the body increases the amount of radiation produced, and shifts it to shorter wavelengths (higher frequencies) in a manner explained only by quantum mechanics.

(physics) the state of a system in which its energy distribution is such that all parts of the system have the same temperature and no heat flows

Of, or relating to the conversion of heat into other forms of energy. / (physics) Of, or relating to thermodynamics.

(physics) The science of the conversions between heat and other forms of energy.

(physics) An electrically charged particle, either an electron or an ion, emitted by a conducting material at high temperatures

(chiefly historical) An electronic device incorporating electrons from a glowing cathode inside an evacuated glass tube, functioning as a switch, amplifier etc.

Concerning the emission of electrons from a heated electrode.

The layer of the Earth's atmosphere directly above the mesosphere and directly below the exosphere.

A device that automatically responds to changes in temperature by activating a heating or cooling system to maintain the temperature at a desired setting.