effusion

American  

[ih-fyoo-zhuhn] / ɪˈfju ʒən /

noun

1. the act of effusing or pouring forth.

2. something that is effused.

3. an unrestrained expression, as of feelings.

   poetic effusions.

4. Pathology.

   1. the escape of a fluid from its natural vessels into a body cavity.

   2. the fluid that escapes.

5. Physics. the flow of a gas through a small orifice at such density that the mean distance between the molecules is large compared with the diameter of the orifice.

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effusion British  

/ ɪˈfjuːʒən /

noun

1. an unrestrained outpouring in speech or words

2. the act or process of being poured out

3. something that is poured out

4. the flow of a gas through a small aperture under pressure, esp when the density is such that the mean distance between molecules is large compared to the diameter of the aperture

5. med

   1. the escape of blood or other fluid into a body cavity or tissue

   2. the fluid that has escaped

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Other Word Forms

• noneffusion
  noun

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Etymology

Origin of effusion

1350–1400; Middle English (< Anglo-French ) < Latin effūsiōn- (stem of effūsiō ), equivalent to ef- ef- + fūsion- fusion

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Explanation

An effusion is an explosion of something, usually words, ideas, or emotions. A popular singer might inspire an effusion of cheers from her devoted fans. Mozart is known for the effusion of notes he could produce at a moment's notice — and all without erasing. A heated argument can produce an effusion of words from both sides. The volcano's eruption was an effusion of smoke and fire. The verb form of the word is effuse: After the high-school musical, your mother effused about your singing. Her comments were an effusion of praise. Your father, on the other hand, was less effusive — but he did like the dancing.

Example Sentences

See Examples For:

effusion

“She developed pleural effusion — fluid between the lungs and ribs — compressing her lungs and making it hard for her to breathe.”

From The Wall Street Journal ● Oct. 5, 2026

She developed pleural effusion — fluid between the lungs and ribs — compressing her lungs and making it hard for her to breathe.

From MarketWatch ● Oct. 5, 2026

In 2019, he underwent surgery for pericardial effusion - a condition affecting the heart.

From BBC ● Aug. 5, 2025

AOM is often confused with otitis media with effusion, or fluid behind the ear, a condition that generally does not involve bacteria and does not benefit from antimicrobial treatment.

From Science Daily ● Mar. 4, 2024

Was it, as “Batty” pretends, a mere effusion of grief?

From "Harry Potter and the Deathly Hallows" by J.K. Rowling

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