diffuser

American  

[dih-fyoo-zer] / dɪˈfyu zər /

Or diffusor

noun

1. a person or thing that diffuses.

2. (in various machines or mechanical systems, as centrifugal pumps or compressors) a device for utilizing part of the kinetic energy of a fluid passing through a machine by gradually increasing the cross-sectional area of the channel or chamber through which it flows so as to decrease its speed and increase its pressure.

3. (in a lighting fixture) any of a variety of translucent materials for filtering glare from the light source.

4. a pierced plate or similar device for distributing compressed air for aeration of sewage.

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diffuser British  

/ dɪˈfjuːzə /

noun

1. a person or thing that diffuses

2. a part of a lighting fixture consisting of a translucent or frosted covering or of a rough reflector: used to scatter the light and prevent glare

3. a cone, wedge, or baffle placed in front of the diaphragm of a loudspeaker to diffuse the sound waves

4. a duct, esp in a wind tunnel or jet engine, that widens gradually in the direction of flow to reduce the speed and increase the pressure of the air or fluid

5. photog a light-scattering medium, such as a screen of fine fabric, placed in the path of a source of light to reduce the sharpness of shadows and thus soften the lighting

6. a perforated plate or similar device for distributing compressed air in the aeration of sewage

7. a device, attached to a hairdryer, which diffuses the warm air as it comes out

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Etymology

Origin of diffuser

First recorded in 1670–80; diffuse + -er ¹

Example Sentences

Mark Myshatyn uses his 3-D printer to create things he needs around the home, such as a light diffuser for photography.

From The Wall Street Journal • Feb. 16, 2026

It disturbs the clean flow of air teams want through the diffuser, the upswept part of the floor at the back of the car.

From BBC • Jul. 22, 2025

Putting essential oils in a diffuser is also an option to revitalize your space.

From Salon • Jan. 1, 2024

Nest New York’s Holiday wall diffuser refill combines pomegranate, mandarin, pine, cloves, cinnamon and vanilla into an aroma that’s spicy and seasonal.

From Washington Times • Dec. 6, 2023

The styling and drying process was extremely complicated—Mari wrapped individual strands of hair around the handle of a comb and then used a hairdryer with a diffuser attachment on each individual curl.

From "Keeping Pace" by Laurie Morrison