[dih-fyoo-zhuh n]


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 formsin·ter·dif·fu·sion, nounnon·dif·fu·sion, nouno·ver·dif·fu·sion, nounre·dif·fu·sion, nounself-dif·fu·sion, noun
Can be confuseddiffraction diffusion reflection rarefaction refraction
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for diffusion

Contemporary Examples of diffusion

Historical Examples of diffusion

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



  • The soft layers are porous, and permit the diffusion of the acid from plate to plate.

  • It is not merely education that makes civilization, but diffusion of education.

  • All of them would be smothered and starved to death as soon as diffusion ceased.

    Common Science

    Carleton W. Washburne

  • It is seeking to combat disease in its centers of diffusion.

    The Ethics of Coperation

    James Hayden Tufts

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
Also called: diffusivity physics 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

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

diffusion in Medicine




The process of diffusing or the condition of being diffused.
The spontaneous intermingling of the particles of two or more substances as a result of random thermal motion.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

diffusion in Science



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.
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 © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

diffusion in Culture


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

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