Merriam-Webster Collegiate Dictionary - silt

 I. noun  Etymology: Middle English cylte, probably of Scandinavian origin; akin to Norwegian dialect sylt beach flooded at high tide; akin to Old High German sulza salt marsh, Old English sealt salt  Date: 15th century  1. loose sedimentary material with rock particles usually 1/20 millimeter or less in diameter; also soil containing 80 percent or more of such ~ and less than 12 percent of clay  2. a deposit of sediment (as by a river)  • ~y adjective  II. verb  Date: 1799  intransitive verb to become choked or obstructed with ~ — often used with up the channel ~ed up  transitive verb to choke, fill, cover, or obstruct with ~ or mud the beaver had ~ed the creek — Hugh Fosburgh  • ~ation noun