What is the meaning of Quenching?

The extinction of any of several physical properties.

The rapid cooling of a hot metal object, by placing it in a liquid, in order to harden it.

A process in which a galaxy loses cold gas, thus strongly suppressing star formation.

The dissipation of energy from light in excess of what can be used for photosynthesis.

present participle and gerund of quench

Source: wiktionary.org