diffuse

American  

[dih-fyooz, dih-fyoos] / dɪˈfyuz, dɪˈfyus /

verb (used with object)

diffuses, present (3rd person singular) diffused, past participle, past diffusing present participle

1. to pour out and spread, as a fluid.

2. to spread or scatter widely or thinly; disseminate.

3. Physics. to spread by diffusion.

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verb (used without object)

diffuses, present (3rd person singular) diffused, past participle, past diffusing present participle

1. to spread.

2. Physics. to intermingle by diffusion.

adjective

1. characterized by great length or discursiveness in speech or writing; wordy.

2. widely spread or scattered; dispersed.

3. Botany. widely or loosely spreading.

4. Optics. (of reflected light) scattered, as from a rough surface (opposed to specular).

diffuse British  

/ dɪˈfjuːzəbəl, dɪˈfjuːslɪ /

verb

1. to spread or cause to spread in all directions

2. to undergo or cause to undergo diffusion

3. to scatter or cause to scatter; disseminate; disperse

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adjective

1. spread out over a wide area

2. lacking conciseness

3. (esp of some creeping stems) spreading loosely over a large area

4. characterized by or exhibiting diffusion

   diffuse light

   diffuse reflection

5. botany (of plant growth) occurring throughout a tissue

Commonly Confused

See defuse

Other Word Forms

Derived Forms

• nondiffused
  adjective
• undiffused
  adjective
• nondiffusing
  adjective
• interdiffuse
  verb
• diffusely
  adverb
• diffusible
  adjective
• overdiffuseness
  noun
• well-diffused
  adjective
• diffuseness
  noun
• rediffuse
  verb
• nondiffuse
  adjective
• diffusibility
  noun
• overdiffuse
  verb
• overdiffusely
  adverb

Conjugated Forms

Present

• has diffused
  perfect 3rd person singular
• have diffused
  perfect
• has been diffusing
  perfect progressive 3rd person singular
• is diffusing
  progressive 3rd person singular
• am diffusing
  progressive 1st person singular
• diffusing
  participle
• are diffusing
  progressive
• have been diffusing
  perfect progressive
• diffuses
  singular 3rd person

Past

• had diffused
  perfect
• diffused
  simple
• were diffusing
  progressive plural
• had been diffusing
  perfect progressive
• was diffusing
  progressive singular
• diffused
  participle

Future

• will diffuse
  simple
• will have diffused
  perfect
• will be diffusing
  progressive
• will have been diffusing
  perfect progressive

Etymology

Origin of diffuse

1350–1400; Middle English (< Anglo-French ) < Latin diffūsus spread, poured forth. See dif-, fuse ²

Explanation

Diffuse means to spread out. Candlelight can diffuse a soft glow throughout a room. A diffuse idea is one that spreads from person to person, and a diffuse speech is scattered and unclear. As a verb, diffuse means to spread something out, but also applies to spreading things such as ideas or culture so that they become widely known. When something is diffused, it's mixed in, and when you drop propaganda pamphlets out of airplanes you're diffusing the propaganda. The adjective comes from Latin diffusus, from diffundere "to pour in different directions," from the prefix dis- "apart" plus fundere, "to pour."

Example Sentences

The Black and Diffuse Auroral Science Surveyor focused on unusual dark regions within auroras known as black auroras.

From Science Daily • Feb. 17, 2026

Diffuse gastric cancer is an inherited disease, and it’s one that he did not wish to pass on.

From Los Angeles Times • Mar. 1, 2023

Diffuse gas in the two galactic haloes would compress on collision, forming a curved structure like the bow wave from a ship moving through water.

From Scientific American • Jan. 12, 2023

“After several days of tests, I have been diagnosed with Diffuse Large B Cell Lymphoma, which is a serious but curable form of cancer,” he said.

From Washington Post • Dec. 28, 2022

The melting ground, the brimming watercourse, The wak'ning air, the birds' returning flight, The longer sunshine, and the shorter night, Arcturus' beams, and Corvus' glitt'ring rays, Diffuse a promise of the genial days.

From Writings in the United Amateur, 1915-1922 by Lovecraft, H. P. (Howard Phillips)