Home › Words › R › radioreactivityradioreactivityradioreactivity means the relative reactivity of cells or organisms to any form of radiation, but especially to the harmful effects of ionizing radiation.EtymologyFrom radio- + reactivity.nounThe relative reactivity of cells or organisms to any form of radiation, but especially to the harmful effects of ionizing radiationDefinitions & examples from Wiktionary (CC BY-SA 3.0).