radioactivity

n. १ (as, the emission of radiant energy) किरणोत्सार (पु.), किरणोत्सारण (न.) २ (as, the property, possessed by some elements as radium, etc., of spontaneously emitting alpha or beta rays and sometimes also gamma rays by the disintegration of nuclei) किरणोत्सारिता (स्त्री.)