Definition of silt in US English:



  • 1Fine sand, clay, or other material carried by running water and deposited as a sediment, especially in a channel or harbor.

    • ‘However, in addition to that alluvium much of central Belfast is underlain instead by a deposit of soft grey mud, silt and fine sand with numerous sea shells, in particular oysters.’
    • ‘Tidal processes constantly winnow the substrate surface in the submerged mouthbar front, and resuspend mud and silt into the water.’
    • ‘Water continuing out over the playa surface carries with it a quantity of fine sand, silt, and clay in suspension.’
    • ‘Excavations in 1990 added weight to the idea that the horse dates from later prehistory as deposits of fine silt in the beak were scientifically dated to the early first millennium BC.’
    • ‘They carry silt which replenishes the topsoil and enables agriculture to flourish.’
    sediment, deposit, alluvium, mud, slime, ooze, sludge
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    1. 1.1 A bed or layer of silt.
      • ‘Carbonaceous plant debris is concentrated in finely laminated silts and mudstones at the tops of some beds.’
      • ‘In fact, badlands occur in a wide range of environments, and on various materials, from marine silts in valleys of the Canadian Arctic to mine-spoil heaps in New Guinea.’
      • ‘The sediments include lacustrine freshwater limestones, silts, marls, occasional sands and local lignite.’
      • ‘These units contain intercalated thin, discontinuous lenses of silts and mudstones, some displaying desiccation cracks.’
      • ‘Under the placic layers were 10s of meters of stratified glaciodeltaic sands and silts.’
    2. 1.2technical Sediment whose particles are between clay and sand in size (typically 0.002–0.06 mm).
      • ‘The textures of soils reflect the proportion of sand, silt, and clay sizes within that portion of an inorganic soil fraction that is less than 2 mm.’
      • ‘There it attaches to particles of minerals (sand, silt, and clay) and organic matter, forming clumps.’
      • ‘The way sand, silt and clay particles are grouped together in aggregates is called the soil structure.’
      • ‘Soil texture, or the proportion of sand, silt and clay particles, directly influences nutrient content, moisture and drainage.’
      • ‘This is soil whose properties are controlled equally by the percentages of clay, silt and sand particles.’


[no object]
  • 1Become filled or blocked with silt.

    ‘the river's mouth had silted up’
    • ‘The towers fall, the rivers silt, the bridges crumble.’
    • ‘The Gonubie River does not have a typically big flushing flow while silting in Transkei rivers is a result of ‘poor land use practice’.’
    • ‘Old Goa remained the colony's capital until I759, when the Mandovi River silted up.’
    • ‘The defendants erected ferry terminals in the Thames, and, as a result, parts of the river bed silted up.’
    • ‘Of course, we would be told that the river has now silted up and that at low tide it would be impossible.’
    become blocked, become choked, become clogged, fill up, fill up with silt, become filled, become dammed
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    1. 1.1with object Fill or block with silt.
      • ‘The lagoon will also have to be dredged as it is heavily silted and the fish are dying because the water is too shallow and the lagoon is not being adequately flushed.’
      • ‘I would mix the soil in the heavily silted water of the Mekong River as a way to spread this handful of soil throughout Vietnam.’
      • ‘Local people cultivate tapioca, rice and vegetables on the heavily silted riverbed.’
      • ‘There are no open drains, fortunately, or they'd be silted by now.’
      • ‘Fish are taken from the river in places where it is badly silted and basically what happens is that they are stripped and hatched to the ova stage.’
      clog, choke, block, jam, obstruct, congest, bung up, dam, dam up, plug, silt up, stop up, seal, fill up, close
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Late Middle English: probably originally denoting a salty deposit and of Scandinavian origin, related to Danish and Norwegian sylt ‘salt marsh’, also to salt.