n. The matter which settles to the bottom of water or any other liquid; settlings; lees; dregs; in geology, detrital material mechanically suspended in or deposited from water; the material of which the sedimentary rocks are composed.n. In a steam-boiler, an internal deposit of precipitate from the feed-water, or of solid matter mechanically present, which lies as a loose or soft mud on the heating surfaces: distinguished from scale, which is a hard crystalline coating adhering to the metal.To allow to settle; settle: said of matter in suspension in a liquid.