nappe
The profile of a body of water flowing over an obstruction in a vertical drop.
Either of the two parts of a double cone.
A sheet-like mass of rock that has been folded over adjacent strata.
The generation of an Alpine mountain range is a matter of piling on the nappes.
Geological nappe whose underside is not in contact with the overflow structure and is at ambient atmospheric pressure.
Where it comes from
From French nappe. Doublet of map, mop, and nape.
Adapted from the Wiktionary entry nappe (CC BY-SA 4.0).