The technique of applying a thin, uneven layer of opaque or semi-opaque paint with a nearly dry brush on top of another layer of dry paint, allowing the color beneath to show through.  Scumbling is often used to soften a color, or to create hazy or textured effects.

Screen Shot 2017-12-29 at 12.54.44 PMClaude Monet. Charing Cross Bridge, London (detail). Oil on canvas. 1899-1901. Saint Louis Art Museum.