sludge

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. Semisolid material such as the type precipitated by sewage treatment.
2. n. Mud, mire, or ooze covering the ground or forming a deposit, as on a riverbed.
3. n. Finely broken or half-formed ice on a body of water, especially the sea.
4. n. An agglutination or aggregation of blood cells forming a semisolid mass that often impedes circulation.
5. v. To agglutinate or aggregate into a semisolid mass; form a sludge. Used of blood cells.

Century Dictionary and Cyclopedia

1. n. Mud; mire.
2. n. A pasty mixture of snow or ice and water; half-melted snow; slush.
3. n. In mining, the fine powder produced by the action of the drill or borer in a bore-hole, when mixed with water, as is usually the case in large and deep bore-holes. The powder when dry is often called bore-meal.
4. n. Refuse from various operations, as from the washing of coal; also, refuse acid and alkali solutions from the agitators, in the refining of crude petroleum: sometimes used, but incorrectly, as the equivalent of slimes, or the very finely comminuted material coming from the stamps. See Slime, 3.
5. n. The more or less viscid mud thrown down from dilute waste soap-liquors of wool-scouring, cotton-bleaching, and dyeing industries when such liquors are treated with crude aluminium sulphate and milk of lime. The remaining effluent is thus in a large measure purified, but the sludge thrown down has usually little value, even as a manure.
6. n. The precipitated solid matter in sewage, usually collected in settling-basins in sewage-disposal works after chemical treatment and filtration. Often pressed into cakes.
7. n. The sediment, in the form of mud, which collects in a steam-boiler.
8. n. Incorrectly, by abbreviation, an opening in a steam-boiler for the removal of sludge or mud; also, the lid which covers such an opening.
9. n. A sand-pump or mud-pumping device for removing sludge from a sink or a bore-hole.
10. n. The silt-like deposit in the bottom of an electrolytic cell.

Wiktionary

1. n. A generic term for solids separated from suspension in a liquid.
2. n. A residual semi-solid material left from industrial, water treatment, or wastewater treatment processes.
3. n. A sediment of accumulated minerals in a steam boiler.
4. n. A mass of small pieces of ice on the surface of a body of water.
5. v. intransitive, informal to slump or slouch.
6. v. intransitive to slop or drip slowly.

GNU Webster's 1913

1. n. Mud; mire; soft mud; slush.
2. n. Small floating pieces of ice, or masses of saturated snow.
3. n. (Mining) See Slime, 4.
4. n. Anything resembling mud or slush; as: (a) A muddy or slimy deposit from sweage. (b) Mud from a drill hole in boring. (c) Muddy sediment in a steam boiler. (d) Settling of cottonseed oil, used in making soap, etc. (e) A residuum of crude paraffin-oil distillation.

WordNet 3.0

1. n. the precipitate produced by sewage treatment
2. n. any thick, viscous matter