diffusion

noun

dif·​fu·​sion di-ˈfyü-zhən 

1

: the state of being spread out or transmitted especially by contact : the action of diffusing

the diffusion of knowledge

2

: prolixity, diffuseness

3

a

chemistry : the process whereby particles of liquids, gases, or solids intermingle as the result of their spontaneous movement caused by thermal (see thermal entry 1 sense 1b) agitation and in dissolved substances move from a region of higher to one of lower concentration

b physics

(1)

: reflection of light by a rough reflecting surface

(2)

: transmission of light through a translucent material : scattering

4

: the spread of cultural elements from one area or group of people to others by contact

5

photography : the softening of sharp outlines in an image

diffusional

di-ˈfyü-zhə-nᵊl 

adjective

Synonyms

• diffuseness
• repetition
• repetitiveness
• periphrasis
• prolixity
• windiness
• garrulity

Examples of diffusion in a Sentence

the author's tendency toward diffusion makes the novel a tedious read

Recent Examples on the Web

The intuitive digital interface is impressive as well, including a one-touch start, adjustable diffusion time and intensity, and use of replaceable signature scent capsules. —Austa Somvichian-Clausen, Robb Report, 14 Aug. 2025

The gaseous diffusion plant, built in 1952, produced enriched uranium as feedstock for the U.S.'s nuclear weapons program and later for use in nuclear power plants, according to the DOE, which owns the site. —Connor Giffin, The Courier-Journal, 6 Aug. 2025

This combination of infrastructure buildout and AI diplomacy aims to position the U.S. as a leader not only through innovation, but through standard setting, global commerce and adoption and diffusion of American technology. —Paulo Carvão, Forbes.com, 23 July 2025

Turning to manufacturing production, the Federal Reserve’s most recent industrial production diffusion index, which provides a reading on manufacturing, mining and public utilities for 296 distinct sectors across six months, is at its highest value in a year. —Bruce Yandle, Boston Herald, 18 July 2025

Word History

Etymology

Middle English diffusioun "outpouring (of speech)," borrowed from Late Latin diffūsiōn-, diffūsiō "pouring out (of liquids), watering of the eyes, abundance" (Latin, "geniality"), from Latin diffud-, variant stem of diffundere "to pour out over a wide surface, spread out, extend" + -tiōn-, -tiō, suffix of verbal action — more at diffuse entry 2

First Known Use

15th century, in the meaning defined at sense 2

Rhymes for diffusion

• allusion
• collusion
• conclusion
• confusion
• contusion
• delusion
• effusion
• exclusion
• extrusion
• illusion
• inclusion
• infusion

Kids Definition

diffusion

noun

dif·​fu·​sion dif-ˈyü-zhən 

1

: a diffusing or a being diffused

2

: the mixing of particles of liquids, gases, or solids so that they move from a region of high concentration to one of lower concentration

3

: the scattering of light by reflection from a rough surface or by passage through a translucent material (as frosted glass)

Medical Definition

diffusion

noun

dif·​fu·​sion dif-ˈyü-zhən 

1

: the process whereby particles of liquids, gases, or solids intermingle as the result of their spontaneous movement caused by thermal agitation and in dissolved substances move from a region of higher to one of lower concentration

2

a

: reflection of light by a rough reflecting surface

b

: transmission of light through a translucent material

diffusional

-ˈyüzh-nəl, -ən-ᵊl 

adjective