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  1. pertaining to actinism.

Origin of actinic

First recorded in 1835–45; actin- + -ic
Related formsac·tin·i·cal·ly, adverbnon·ac·tin·ic, adjectivenon·ac·tin·i·cal·ly, adverbun·ac·tin·ic, adjective
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for actinic

Historical Examples

  • But the figure passed beyond the actinic glare and vanished.

    Astounding Stories of Super-Science, March 1930


  • They were terrific words too, from aortic and actinic 232 in the a's to genuflections in the g's.

    The Annals of Ann

    Kate Trimble Sharber

  • For this reason, it is obvious that it must not be carelessly exposed to actinic light.

  • In what season of the year is the actinic power of light the greatest?

  • Because of the actinic, or chemical power of the rays of the sun.

British Dictionary definitions for actinic


  1. (of radiation) producing a photochemical effect
Derived Formsactinically, adverbactinism, noun

Word Origin

C19: from actino- + -ic
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

actinic in Medicine


  1. Of or relating to the chemically active rays of the electromagnetic spectrum.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.