D defs.my
Entry 1 sense Webster, 1913

Actinism

· Ac·tin·ism · IPA
01 n. The property of radiant energy (found chiefly in solar or electric light) by which chemical changes are produced, as in photography.
  1. 1.
    The property of radiant energy (found chiefly in solar or electric light) by which chemical changes are produced, as in photography.