Definition of "diffuser" [dif•fus•er]

• One that diffuses, as: (noun)
• A light fixture, such as a frosted globe, that spreads light evenly. (noun)
• A medium that scatters light, used in photography to soften shadows. (noun)
• A device, such as a cone or baffle, placed in front of a loudspeaker diaphragm to diffuse the sound waves. (noun)
• A flow passage in a wind tunnel that decelerates a stream of gas or liquid from a high to a low velocity. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "The upper deck of a double-decker diffuser is fed by airflow from apertures located underneath the car, in the vertical wall joining the step plane and the reference plane."
• "A polycarbonate and acrylic diffuser is positioned in the centre."
• "To cure this, we can add a bigger "diffuser" - a piece of bodywork shaped to channel air out from underneath the car in a controlled way."