sediment
n. C / Un. solid material that settles at the bottom of a liquid. You often see it as sand or mud at the bottom of a river or as tiny bits at the bottom of a bottle of wine.
n. matter that settles to the bottom of a liquid; also, solid material that is moved and deposited in a new location by water, ice, or wind.
There was a layer of sediment at the bottom of the lake.
The river carries heavy sediment downstream, which eventually builds up and creates new land in the delta.
Geologists analyze layers of ancient sediment to understand how the local climate and sea levels have shifted over millions of years.
From Middle French sédiment, from Latin sedimentum < sedeō.
Uncountable when referring to the substance in general; countable when referring to specific layers or types of deposited material.