SCUMBLE

I. transitive verb (~d; scumbling) Etymology: perhaps frequentative of 2scum Date: 1798 1. to make (as color or a painting) less brilliant by covering with a thin coat of opaque or semiopaque color applied with a nearly dry brush, to apply (a color) in this manner, to soften the lines or colors of (a drawing) by rubbing lightly, II. noun Date: 1834 the act or effect of scumbling, a material used for scumbling