You can find some info here
https://help.quixel.com/hc/en-us/articles/115000612165-What-maps-are-included-and-how-do-I-use-them-
Depending on what you are doing, you can use that map to drive Sheen for example.
Fuzz represents a mask for a rough, “fuzzy” surface such as moss. This is an optional bonus map, and can be applied to give extra diffusion to a surface.
Workflow: Metalness / Specular
Context: Real-time / Offline
Characteristics: Bright color = Fuzzy, Dark Color = Clear
This is exactly what I am looking for but what does it translate to in Arnold