1a board made of ridged wood or a sheet of corrugated zinc, used when washing clothes as a surface against which to scrub them. a washboard played as a percussion instrument by scraping. North American the surface of a worn, uneven road. [as modifier] denoting a man’s stomach that is lean and has well-defined muscles.
2a board fixed along the side of a boat to prevent water from spilling in over the edge.
verb [with object] (usually as adjective washboarded) chiefly North American
cause ridges to develop in (a road or road surface):a road left washboarded by winter frost