[verb ih-rey-dee-eyt; adjective ih-rey-dee-it, -eyt]
verb (used with object), ir·ra·di·at·ed, ir·ra·di·at·ing.
  1. to shed rays of light upon; illuminate.
  2. to illumine intellectually or spiritually.
  3. to brighten as if with light.
  4. to radiate (light, illumination, etc.).
  5. to heat with radiant energy.
  6. to treat by exposure to radiation, as of ultraviolet light.
  7. to expose to radiation.
verb (used without object), ir·ra·di·at·ed, ir·ra·di·at·ing.
  1. Archaic.
    1. to emit rays; shine.
    2. to become radiant.
  1. irradiated; bright.

Origin of irradiate

1595–1605; < Latin irradiātus, past participle of irradiāre to shine upon. See ir-1, radiate
Related formsir·ra·di·at·ing·ly, adverbir·ra·di·a·tive, adjectiveir·ra·di·a·tor, nounnon·ir·ra·di·at·ed, adjectiveun·ir·ra·di·at·ed, adjectiveun·ir·ra·di·a·tive, adjective Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

British Dictionary definitions for irradiator


  1. (tr) physics to subject to or treat with light or other electromagnetic radiation or with beams of particles
  2. (tr) to expose (food) to electromagnetic radiation to kill bacteria and retard deterioration
  3. (tr) to make clear or bright intellectually or spiritually; illumine
  4. a less common word for radiate (def. 1)
  5. (intr) obsolete to become radiant
Derived Formsirradiative, adjectiveirradiator, noun
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

Word Origin and History for irradiator



c.1600, "to cast beams of light upon," from Latin irradiatus, past participle of irradiare "shine forth," from assimilated form of in- "into, in" (see in- (2)) + radiare "to shine" (see radiate). Meaning "expose to radiation other than light" (originally X-rays) is from 1901. Related: Irradiated; irradiating.

Online Etymology Dictionary, © 2010 Douglas Harper

irradiator in Medicine


  1. To expose to radiation, as for diagnostic or therapeutic purposes.
  2. To treat with radiation.
  3. To apply radiation to a structure or organism.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

irradiator in Science


  1. To expose to or treat with radiation. For example, meat sold as food is often irradiated with x-rays or other radiation to kill bacteria; uranium 238 can be irradiated with neutrons to create fissionable plutonium 239.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.