diffusion
Americannoun
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the act of diffusing or state of being diffused.
During the gradual, unorchestrated diffusion of ideas from science into the surrounding culture, crucial information can sometimes be lost.
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excessive wordiness of speech or writing; long-windedness.
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Physics.
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Also called migration. an intermingling of molecules, ions, etc., resulting from random thermal agitation, as in the dispersion of a vapor in air.
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a reflection or refraction of light or other electromagnetic radiation from an irregular surface, or an erratic dispersion through a surface; scattering.
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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.
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Meteorology. the spreading of atmospheric constituents or properties by turbulent motion as well as molecular motion of the air.
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Also called cultural diffusion. Anthropology, Sociology. the transmission of elements or features of one culture to another.
noun
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the act or process of diffusing or being diffused; dispersion
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verbosity
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physics
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the random thermal motion of atoms, molecules, clusters of atoms, etc, in gases, liquids, and some solids
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the transfer of atoms or molecules by their random motion from one part of a medium to another
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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
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Also called: diffusivity. physics the degree to which the directions of propagation of reverberant sound waves differ from point to point in an enclosure
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anthropol the transmission of social institutions, skills, and myths from one culture to another
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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.
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Compare osmosis
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The reflection or refraction of radiation such as light or sound by an irregular surface, tending to scatter it in many directions.
Other Word Forms
Derived Forms
Etymology
Origin of diffusion
First recorded in 1325–75; Middle English, from Latin diffūsiōn-, stem of diffūsiō “a spreading out”; equivalent to diffuse + -ion
Explanation
Diffusion is the act of dispersing something, spreading it out from a central point. When an idea catches on, that's a type of diffusion. When you spray air freshener and the scent spreads from a tight space to fill a larger one, that's diffusion. In science, diffusion is a physical process of atoms or molecules moving apart within a gas or liquid. You can also use the word diffusion to describe the spreading of information. Ever notice how a trendy word or band will suddenly be everywhere, even though nobody heard of it last week? That's diffusion. This word means something similar to dispersal and dissemination.
Vocabulary lists containing diffusion
Cell Biology - Middle School
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Life Science: Cell Biology
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Human Geography - High School
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Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
Howe Institute think tank’s business-cycle council, the recognized arbiter of declaring a recession, said it was premature to describe the current downturn as such because it lacked depth and diffusion.
From The Wall Street Journal • Jun. 10, 2026
Unlike surround-sound in movie theaters which pinpoints directionality, the result here was diffusion — not eavesdropping but pure immersion.
From Los Angeles Times • May 28, 2026
Throughout history the diffusion of technology has democratized information and improved living standards, especially for the poor.
From The Wall Street Journal • May 27, 2026
“AI diffusion is accelerating and our addressable market, customer base, and platform are all expanding rapidly,” he said.
From Barron's • May 7, 2026
Related to these factors affecting diffusion within continents is a third set of factors influencing diffusion between continents, which may also help build up a local pool of domesticates and technology.
From "Guns, Germs, and Steel: The Fates of Human Societies" by Jared M. Diamond
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
