sludge

Etymology

Possibly related to slush.

noun

1. Solids separated from suspension in a liquid.
   Floods in northern India, mostly in the small state of Uttarakhand, have wrought disaster on an enormous scale.[…]Rock-filled torrents smashed vehicles and homes, burying victims under rubble and sludge. 2013-06-29, “High and wet”, in The Economist, volume 407, number 8842, page 28
2. A residual semi-solid material left from industrial, water treatment, or wastewater treatment processes.
3. A sediment of accumulated minerals in a steam boiler.
4. A mass of small pieces of ice on the surface of a body of water.
5. (uncountable, music) sludge metal

verb

1. (intransitive, informal) To slump or slouch.
2. (intransitive) To slop or drip slowly.