extinctionn.[L. extinctio, exstinction: cf. F. extinction.]1. 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.()2. State of being extinguished or of ceasing to be; destruction; suppression; as, the extinction of life, of a family, of a quarrel, of claim.()3. 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.()()