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[dih-fyoo-zhuh n] /dɪˈfyu ʒən/
act of diffusing; state of being diffused.
prolixity of speech or writing; discursiveness.
  1. Also called migration. an intermingling of molecules, ions, etc., resulting from random thermal agitation, as in the dispersion of a vapor in air.
  2. a reflection or refraction of light or other electromagnetic radiation from an irregular surface or an erratic dispersion through a surface; scattering.
Movies. a soft-focus effect resulting from placing a gelatin or silk plate in front of a studio light or a camera lens, or through the use of diffusion filters.
Meteorology. the spreading of atmospheric constituents or properties by turbulent motion as well as molecular motion of the air.
Anthropology, Sociology.. Also called cultural diffusion. the transmission of elements or features of one culture to another.
Origin of diffusion
1325-75; Middle English < Latin diffūsiōn- (stem of diffūsiō) a spreading out, equivalent to diffūs(us) (see diffuse) + -iōn- -ion
Related forms
interdiffusion, noun
nondiffusion, noun
overdiffusion, noun
rediffusion, noun
self-diffusion, noun
Can be confused Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2017.
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Examples from the Web for diffusion
Contemporary Examples
Historical Examples
  • It is by this sort of diffusion that chicks which are being incubated get air, and that growing plants get food.

    Common Science Carleton W. Washburne
  • If less than one inch, however, the diffusion of light is not so good.

  • It has also many noble charitable organizations and societies for the diffusion of science.

    Foot-prints of Travel Maturin M. Ballou
  • You objects that call from diffusion my meanings and give them shape!

    Practical Mysticism Evelyn Underhill
  • For diffusion as for light the shorter waves are the most refracted.

    The Mechanism of Life Stphane Leduc
  • Like man, he must have a purpose; and his purpose is the diffusion of that goodness or good which he himself is.

    Timaeus Plato
  • Fig. 20 shows the aspect after two minutes, when the diffusion is almost complete.

    The Mechanism of Life Stphane Leduc
British Dictionary definitions for diffusion


the act or process of diffusing or being diffused; dispersion
  1. the random thermal motion of atoms, molecules, clusters of atoms, etc, in gases, liquids, and some solids
  2. the transfer of atoms or molecules by their random motion from one part of a medium to another
(physics) the transmission or reflection of electromagnetic radiation, esp light, in which the radiation is scattered in many directions and not directly reflected or refracted; scattering
(physics) Also called diffusivity. the degree to which the directions of propagation of reverberant sound waves differ from point to point in an enclosure
(anthropol) the transmission of social institutions, skills, and myths from one culture to another
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
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Contemporary definitions for diffusion's 21st Century Lexicon
Copyright © 2003-2014, LLC
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Word Origin and History for diffusion

late 14c., from Latin diffusionem (nominative diffusio) "a pouring forth," noun of action from past participle stem of diffundere "scatter, pour out," from dis- "apart, in every direction" (see dis-) + fundere "pour" (see found (v.2)).

Online Etymology Dictionary, © 2010 Douglas Harper
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diffusion in Medicine

diffusion dif·fu·sion (dĭ-fyōō'zhən)

  1. The process of diffusing or the condition of being diffused.

  2. The spontaneous intermingling of the particles of two or more substances as a result of random thermal motion.

  3. See dialysis.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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diffusion in Science
  1. The movement of atoms or molecules from an area of higher concentration to an area of lower concentration. Atoms and small molecules can move across a cell membrane by diffusion. Compare osmosis.

  2. The reflection or refraction of radiation such as light or sound by an irregular surface, tending to scatter it in many directions.

The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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diffusion in Culture

diffusion definition

The spreading of atoms or molecules of one substance through those of another, especially into liquids or gases.

The American Heritage® New Dictionary of Cultural Literacy, Third Edition
Copyright © 2005 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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