Pronunciation: (di-fyOO'zur),[key] —n. 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. Also,diffusor.