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

Balmain signs licenses for men’s outerwear and casualwear and launches the B Balmain diffusion line, designed by Christiane Bailly. —Lily Templeton, Footwear News, 19 Sep. 2025

In one more example of investment strategy, the ISSA believes hitting certain metrics for diffusion of its product will create value for broadcasting future Games, which will in turn generate interest, excitement, and young athletes who will go on to compete at future Games. —Blythe Lawrence, Forbes.com, 18 Sep. 2025

The diffusion index in the jobs report gauges the concentration of growth. —Jason Ma, Fortune, 7 Sep. 2025

Over the years, Armani launched a popular diffusion line, Emporio Armani, as well as other successful spin-offs such as Armani Jeans, Armani Exchange and the home interiors brand Armani/Casa. —Kati Chitrakorn, CNN Money, 4 Sep. 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