Merriam-Webster Logo
  • Dictionary
  • Thesaurus
  • Medical
  • Scrabble
  • Spanish Central
  • Learner's Dictionary


adjective dif·fuse \di-ˈfyüs\

Simple Definition of diffuse

  • : spread out over a large space : not concentrated in one area

Full Definition of diffuse

  1. 1 :  being at once verbose and ill-organized <a diffuse report from the scene of the earthquake>

  2. 2 :  not concentrated or localized <diffuse lighting><diffuse sclerosis>

dif·fuse·ly adverb
dif·fuse·ness noun

Examples of diffuse

  1. The forest was filled with a soft, diffuse light.

  2. <a diffuse speech that took a great deal of time to make a very small point>

Origin of diffuse

Middle English, from Latin diffusus, past participle of diffundere to spread out, from dis- + fundere to pour — more at found

First Known Use: 15th century

Synonym Discussion of diffuse

wordy, verbose, prolix, diffuse mean using more words than necessary to express thought. wordy may also imply loquaciousness or garrulity <a wordy speech>. verbose suggests a resulting dullness, obscurity, or lack of incisiveness or precision <the verbose position papers>. prolix suggests unreasonable and tedious dwelling on details <habitually transformed brief anecdotes into prolix sagas>. diffuse stresses lack of compactness and pointedness of style <diffuse memoirs that are so many shaggy-dog stories>.



verb dif·fuse \di-ˈfyüz\

Simple Definition of diffuse

  • : to spread out : to move freely throughout a large area

  • : to exist or be known throughout an area

  • : to cause (light) to be soft and spread out

Full Definition of diffuse


  1. transitive verb
  2. 1 a :  to pour out and permit or cause to spread freely b :  extend, scatter c :  to spread thinly or wastefully

  3. 2 :  to subject to diffusion; especially :  to break up and distribute (incident light) by reflection

  4. intransitive verb
  5. 1 :  to spread out or become transmitted especially by contact

  6. 2 :  to undergo diffusion

dif·fus·ible play \di-ˈfyü-zə-bəl\ adjective

Examples of diffuse

  1. The heat from the radiator diffuses throughout the room.

  2. The heat was diffused throughout the room.

  3. The photographer uses a screen to diffuse the light.

  4. an area of diffused light

Origin of diffuse

Middle English diffused, past participle, from Latin diffusus, past participle

First Known Use: 14th century

Seen and Heard

What made you want to look up diffuse? Please tell us where you read or heard it (including the quote, if possible).


February 6, 2016

an official order, decree, or edict

Get Word of the Day daily email!


Take a 3-minute break and test your skills!


Which of the following refers to thin, bending ice, or to the act of running over such ice?

spindrift pince-nez kittly-benders duvet
Name That Thing

10 quick questions: hear them, spell them, and see how your skills compare to the crowd.


Test Your Knowledge - and learn some interesting things along the way.