corrasion (cor-ra'-sion). (a) A process of erosion whereby rocks and soil are mechanically removed or worn away by the abrasive action of solid materials moved along by wind, waves, running water, glaciers, or gravity; e.g., the wearing-away of the bed and banks of a stream by the cutting, scraping, scratching, and scouring effects of a sediment load carried by the stream, or the sawing and grinding action of sand, gravel, and boulders hurled by waves and currents against a shore. The term has also been used for the loosening of rock material by the impact of rushing water itself, and was used by Penck (1953, p.112) for the "freeing of loosened rock fragments from their place of origin". The term "abrasion" is essentially synonymous. Syn: mechanical erosion. (b) A term sometimes used as a syn. of attrition. (c) A term formerly used as a syn. of corrosion, or as including the work of corrosion. The term was first used by Powell (1875, p.205) for channel cutting or the deepening of any valley floor and was extended by Gilbert (1877, p.101) to the work of all running water (including lateral corrasion). Verb: corrade.