In the 'Savvy' series of books the word "scumble" is used in what I think is an original way. I have the sense it relates to using the savvy abilities the characters have, but I'm not sure what an exact definition would be.
A definition from Google is:
verb: modify (a painting or color) by applying a very thin coat of opaque paint to give a softer or duller effect. "the area surrounding the main figures will be scumbled"
noun: a thin, opaque coat of paint or layer of shading applied to give a softer or duller effect.
This doesn't seem relevant unless in some metaphorical sense?