D defs.my
Entry 2 senses Webster, 1913

radioactive

/(rā`dĭ*ō̇*ăk"tĭv)/ · ra·di·o·ac·tive · IPA /ˌɹeɪdioʊˈæktɪv/
01 a. Capable of luminescence under the action of cathode rays, X rays, or any of the allied forms of radiation.
  1. 1.
    Capable of luminescence under the action of cathode rays, X rays, or any of the allied forms of radiation.(Physics) [obsolete]
  2. 2.
    of, exhibiting, or caused by radioactivity.(Physics) See: radioactivity