Princeton's WordNet

1. radiation(noun)

   energy that is radiated or transmitted in the form of rays or waves or particles

2. radiation(noun)

   the act of spreading outward from a central source

3. radiation sickness, radiation syndrome, radiation(noun)

   syndrome resulting from exposure to ionizing radiation (e.g., exposure to radioactive chemicals or to nuclear explosions); low doses cause diarrhea and nausea and vomiting and sometimes loss of hair; greater exposure can cause sterility and cataracts and some forms of cancer and other diseases; severe exposure can cause death within hours

   "he was suffering from radiation"

4. radiation, radioactivity(noun)

   the spontaneous emission of a stream of particles or electromagnetic rays in nuclear decay

5. radiation(noun)

   the spread of a group of organisms into new habitats

6. radiation(noun)

   a radial arrangement of nerve fibers connecting different parts of the brain

7. radiotherapy, radiation therapy, radiation, actinotherapy, irradiation(noun)

   (medicine) the treatment of disease (especially cancer) by exposure to a radioactive substance

Kernerman English Learner's Dictionary

1. radiation(noun)ˌreɪ diˈeɪ ʃən

   energy produced by a nuclear reaction

   dangerous levels of radiation

2. radiationˌreɪ diˈeɪ ʃən

   rays of energy produced by heat, light, etc.

   cell phone radiation hazards

Wiktionary

1. radiation(Noun)

   The shooting forth of anything from a point or surface, like the diverging rays of light; as, the radiation of heat.

2. radiation(Noun)

   The process of radiating waves or particles.

3. radiation(Noun)

   The transfer of energy via radiation (as opposed to convection or conduction)

4. radiation(Noun)

   Radioactive energy

Origin: From radiatio.

Webster Dictionary

1. Radiation(noun)

   the act of radiating, or the state of being radiated; emission and diffusion of rays of light; beamy brightness

2. Radiation(noun)

   the shooting forth of anything from a point or surface, like the diverging rays of light; as, the radiation of heat

U.S. National Library of Medicine

1. Radiation

   Emission or propagation of electromagnetic energy (waves/rays), or the waves/rays themselves; a stream of electromagnetic particles (electrons, neutrons, protons, alpha particles) or a mixture of these. The most common source is the sun.

The Standard Electrical Dictionary

1. Radiation

   The traveling or motion of ether waves through space. [Transcriber's note: The modern term corresponding to this definition is photons. The modern concept of radiation also includes particles-- neutrons, protons, alpha (helium) and beta (electrons) rays and other exotic items.]

• bestralingAfrikaans
• إشْعاعArabic
• излъчванеBulgarian
• radiaçãoPortuguese (BR)
• vyzařováníCzech
• die AusstrahlungGerman
• strålingDanish
• ακτινοβολίαGreek
• radiaciónSpanish
• kiirgusEstonian
• تابشFarsi
• säteilyFinnish
• radiationFrench
• קְרִינָהHebrew
• प्रकाश या अन्य किरणों का विकिरणHindi
• radijacija, isijavanjeCroatian
• sugárzásHungarian
• radiasiIndonesian
• geislunIcelandic
• radiazioneItalian
• 放射Japanese
• 방사선Korean
• spinduliavimas, spinduliuotė, radiacijaLithuanian
• radiācija; starojumsLatvian
• pancaran radiasiMalay
• uitstralingDutch
• utstråling, strålingNorwegian
• promieniowaniePolish
• تابشPersian
• وړانګى اچونه، پړ كيدنه، بريښدنه، ځلونهPashto
• radiaçãoPortuguese
• radiaţieRomanian
• излучениеRussian
• vyžarovanieSlovak
• žarčenjeSlovenian
• radijacijaSerbian
• [ut]strålningSwedish
• รังสีThai
• radyasyonTurkish
• 輻射Chinese (Trad.)
• випромінювання, радіаціяUkrainian
• درخشانیUrdu
• sự tỏa chiếuVietnamese
• 辐射Chinese (Simp.)