extinction

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The act of extinguishing.
• noun The condition of being extinguished.
• noun The fact of being extinct or the process of becoming extinct.
• noun Psychology A reduction or a loss in the strength or rate of a conditioned response when the unconditioned stimulus or reinforcement is withheld.
• noun Physiology A gradual decrease in the excitability of a nerve to a previously adequate stimulus, usually resulting in total loss of excitability.
• noun Astronomy The dimming of celestial objects, usually measured in magnitudes, due to scattering and absorption of their light as it passes through interstellar dust clouds and the earth's atmosphere.

from The Century Dictionary.

• noun The act of extinguishing, or the state of being extinguished; a quenching or putting out, as of fire or flame.
• noun Hence A bringing or coming to an end; a putting out of existence; suppression; destruction.
• noun In optics, the arresting of a beam of light by polarization, by the imperfect transparency of the medium, or otherwise.

from the GNU version of the Collaborative International Dictionary of English.

• noun The act of extinguishing or making extinct; a putting an end to; the act of putting out or destroying light, fire, life, activity, influence, etc.
• noun State of being extinguished or of ceasing to be; destruction; suppression.
• noun The ceasing to exist of a species of living organism, such as a plant or animal, whose numbers declined to the point where the last member of the species died and therefore no new members of the species could ever again be born.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun The action of making or becoming extinct; annihilation.
• noun astronomy The absorption or scattering of electromagnetic radiation emitted by astronomical objects by intervening dust and gas before it reaches the observer.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun the reduction of the intensity of radiation as a consequence of absorption and radiation
• noun no longer active; extinguished
• noun complete annihilation
• noun no longer in existence
• noun the act of extinguishing; causing to stop burning
• noun a conditioning process in which the reinforcer is removed and a conditioned response becomes independent of the conditioned stimulus