- 1. The subjective enlargement of a bright object seen against a dark background. 2. Exposure to the action of electromagnetic radiation ( e.g., heat, light, x-rays). 3. The spreading of nervous impulses from one area in the brain or cord, or from a tract, to another tract. SEE ALSO: radiation. [L. ir-radio, (in-r), pp. -radi-atus, to beam forth]
* * *ir·ra·di·a·tion ir-.ād-ē-'ā-shən n1 a) the radiation of a physiologically active agent from a point of origin within the body esp the spread of a nervous impulse beyond the usual conduction pathb) apparent enlargement of a light or bright object or surface when displayed against a dark background2 a) exposure to radiation (as ultraviolet light, X-rays, or alpha particles)b) application of radiation (as X-rays or gamma rays) esp. for therapeutic purposes3) IRRADIANCE
* * *n.1. exposure of the body's tissues to ionizing radiation (see ionization). The source may be background radiation, diagnostic X-rays, radiotherapy, or nuclear accidents.2. exposure of a substance or object to ionizing radiation. Irradiation of food with gamma rays, which kill bacteria, is a technique used in food preservation.
* * *ir·ra·di·a·tion (ĭ-ra″de-aґshən) [ir- + radiation] 1. radiotherapy. 2. the dispersion of nervous impulse beyond the normal path of conduction. 3. the application of rays, such as ultraviolet rays, to a substance to increase its vitamin efficiency and shelf life. 4. a phenomenon in which, owing to the difference in the illumination of the field of vision, objects appear to be much larger than they really are.
Medical dictionary. 2011.