diffuser

1 :  one that diffuses: such asa :  a device (such as a reflector) for distributing the light of a lamp evenlyb :  a screen (as of cloth or frosted glass) for softening lighting (as in photography)c :  a device (such as slats at different angles) for deflecting air from an outlet in various directions

2 :  a device for reducing the velocity and increasing the static pressure of a fluid passing through a system