- the act or process of diffusing or being diffused; dispersion
- verbosity
- the random thermal motion of atoms, molecules, clusters of atoms, etc, in gases, liquids, and some solids
- the transfer of atoms or molecules by their random motion from one part of a medium to another
- 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
- the transmission of social institutions, skills, and myths from one culture to another
WordReference Random House Unabridged Dictionary of American English © 2026
dif•fu•sion
(di fyo̅o̅′zhən),USA pronunciation n.
- act of diffusing;
state of being diffused. - prolixity of speech or writing;
discursiveness. - Physics
- PhysicsAlso called migration. an intermingling of molecules, ions, etc., resulting from random thermal agitation, as in the dispersion of a vapor in air.
- a reflection or refraction of light or other electromagnetic radiation from an irregular surface or an erratic dispersion through a surface;
scattering.
- Cinema[Motion Pictures.]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.
- Meteorologythe spreading of atmospheric constituents or properties by turbulent motion as well as molecular motion of the air.
- Anthropology, Sociologythe transmission of elements or features of one culture to another.
- Latin diffūsiōn- (stem of diffūsiō) a spreading out, equivalent. to diffūs(us) (see diffuse) + -iōn- -ion
- Middle English 1325–75
Collins Concise English Dictionary © HarperCollins Publishers::
diffusion /dɪˈfjuːʒən/ n
dif•fuse /v. dɪˈfyuz; adj. -ˈfyus/USA pronunciation
v., -fused, -fusing, adj.
v.
adj.
dif•fuse•ness, n. [uncountable]
dif•fu•sion /dɪˈfyuʒən/USA pronunciation n. [uncountable]diffusion of gases into the atmosphere.
dif•fu•sive /dɪˈfyusɪv/USA pronunciation adj. See -fus-.
WordReference Random House Unabridged Dictionary of American English © 2026v.
- to (cause to) spread or scatter widely: [no object]The light diffused into the room.[~ + object]Diffuse the light in your room to avoid glare.
- Physics to spread out freely without restriction;
disseminate:[~ + object]The printing press helped diffuse knowledge.
adj.
- widely spread or scattered;
dispersed:The room was bathed in soft, diffuse light. - characterized by wordiness in speech or writing;
disjointed:I got lost in your rather diffuse essay.
dif•fuse•ness, n. [uncountable]
dif•fu•sion /dɪˈfyuʒən/USA pronunciation n. [uncountable]diffusion of gases into the atmosphere.
dif•fu•sive /dɪˈfyusɪv/USA pronunciation adj. See -fus-.
dif•fuse
(v. di fyo̅o̅z′;adj. di fyo̅o̅s′),USA pronunciation v., -fused, -fusing, adj.
v.t.
v.i.
adj.
dif•fuse•ly
(di fyo̅o̅s′lē),USA pronunciation adv.
dif•fuse′ness, n.
v.t.
- to pour out and spread, as a fluid.
- to spread or scatter widely or thinly;
disseminate. - Physicsto spread by diffusion.
v.i.
- to spread.
- Physicsto intermingle by diffusion.
adj.
- characterized by great length or discursiveness in speech or writing;
wordy. - widely spread or scattered;
dispersed. - Botanywidely or loosely spreading.
- Optics(of reflected light) scattered, as from a rough surface (opposed to specular).
- Latin diffūsus spread, poured forth. See dif-, fuse2
- Anglo-French)
- Middle English (1350–1400
'diffusion' also found in these entries (note: many are not synonyms or translations):
atmolysis
- dialysis
- diffuse
- diffusive
- Graham
- mirror
- osmosis
- permeate
- Perrin
- photolithography
- spread
- whispering campaign
- charge
- culture diffusion
- diffusionism
- electrodialysis
- gaseous diffusion
- Graham's law of diffusion
- hemorrhage
- Holophane
- homogenize
- horizontal mobility
- hyaluronidase
- immunodiffusion
- lag
- migration
- propagation
- thermal diffusion
- thermodiffusion
- vertical mobility
- self-diffusion
- Smithsonian Institution