n.1. Semisolid material such as the type precipitated by sewage treatment.
2. Mud, mire, or ooze covering the ground or forming a deposit, as on a riverbed.
3. Finely broken or half-formed ice on a body of water, especially the sea.
4. A semisolid mass composed of an aggregation of cells (such as red blood cells in blood vessels) or particulate matter (such as cholesterol crystals and calcium salts in bile).